July 14, 2012 New details emerging about what Syrian activists called a massacre of civilians near the central city of Hama indicated that it was more likely an uneven clash between the heavily armed Syrian military and local fighters bearing light weapons. A report by United Nations observers seemed to indicate that some people had been killed at close range — it said there were pools of blood and blood spatters in several houses along with bullet cases. The team also found a burned school and damaged houses. The number of casualties remained unclear.

July 16, 2012 New fighting was reported in the Syrian capital, Damascus, as Russia made clear that the Kremlin has no intention of supporting a British proposal to enact United Nations sanctions as a solution to the Syrian crisis.

July 17, 2012 Antigovernment activists reported a third day of street battles in the Syrian capital of Damascus as rebels fought Syrian Army forces in several restive neighborhoods near the edge of the old city. The security forces were backed by helicopter gunships, in an apparent hardening of the government’s response.

July 18, 2012 President Bashar al-Assad’s brother-in-law and Syria’s defense minister were killed when a suicide bomber attacked a crisis group of senior ministers and security chiefs meeting in central Damascus, according to state television and activists.

July 19, 2012 Fighting seized neighborhoods encircling Damascus for a fifth straight day, as the impact of of the suicide bombing that killed two of President Bashar al-Assad’s key security aides continued to reverberate. Opposition activists reported battles between the Army and opposition forces in the southern district of the city and in the northern suburb of Qaboun, with residents who were not trapped by fighting fleeing many areas.

July 20, 2012 Government forces claimed to have retaken a pocket of Damascus a day after rebel fighters, building on the momentum gained by their brazen assassination of top security officials, seized all four border crossings with Iraq and one into Turkey. Iraq reported to have thrown up blast walls to seal its main border crossing with Syria while thousands of Syrians fled toward Lebanon.

July 22, 2012 Violent clashes continued in neighborhoods of Aleppo and Damascus, Syria’s two main cities, as Syrian government forces fought to regain  control over areas that rebels claimed to have seized in recent days. In Damascus, the government maintained its effort to mop up pockets of rebel fighters who had moved close to the center of the capital. Fighting was heavy in the neighborhoods of Barzeh and Mezze, activists said.

July 23, 2012 The Syrian government said that its forces would never use chemical weapons in its domestic conflict. The government said it would use them only in case of an external attack, according to Jihad Makdissi, the Foreign Ministry spokesman. The European Union also strengthened its arms embargo against Syria and toughened sanctions against supporters of the country’s president.

July 24, 2012 Syrian armed forces battling insurgents in Aleppo, Syria’s second-largest city, bombed its eastern areas with fighter jets, according to a BBC correspondent traveling with the insurgents. If confirmed, the use of warplanes would signify an escalation by the Syrian government in its effort to crush armed resistance.

July 25, 2012 In Aleppo, Syria’s sprawling commercial capital, a major confrontation was brewing between the government and insurgents, with hundreds of fighters from both sides streaming into the city and taking up positions in or around half a dozen neighborhoods where the rebels have dominated for days. Government soldiers transported via trucks and buses deployed around the city’s historic 13th-century citadel, and thousands more were en route, according to rebel fighters and activists.

July 26, 2012 Government forces maintained their shelling of key cities, with Aleppo in particular bracing for a anticipated showdown between rebel fighters expanding into more neighborhoods and government military reinforcements who have yet to materialize. It was not exactly the calm before the storm, as fierce street fights have led to deaths on both sides. Most of the fighting is taking place in the poorer, eastern parts of Aleppo, which is populated mainly by Sunni Muslims, who are sympathetic to the fighters.

July 27, 2012 Syrian Army helicopters fired on neighborhoods in Aleppo, activists said, as the army readied assault troops and armored columns for a possible invasion of the city.

July 28, 2012 The Syrian Army stepped up its barrage on Aleppo, particularly the Salaheddiin neighborhood, residents and activists said. Also, Russian Foreign Minister Sergey V. Lavrov called on Mr. Assad’s government to “make the first moves” in ceasing military action. But he also blamed Western countries and some of Syria’s neighbors for not putting enough pressure on the armed opposition to stop fighting.

July 29, 2012 As fierce fighting continued in Aleppo and its outskirts, the Syrian foreign minister, on a visit to Iran, lashed out at Saudi Arabia, Qatar and Turkey, blaming them for the escalation of violence and saying that their backing of armed groups in Syria was blocking a path toward “political dialogue.” The comments by Walid al-Moallem were an echo of those made by Syria’s most important ally, Russia.

July 30, 2012 Both the Syrian government and its opponents claimed victories in the embattled city of Aleppo, a day after the United Nations humanitarian chief warned of a growing crisis in the country’s largest city, saying that almost of a tenth of its residents had fled over two days of fighting. Opposition fighters said that after a pitched battle with the Syrian Army, they had seized control of a vital checkpoint a few miles northwest of the city, freeing up a route for supplies and fighters between Aleppo and the Turkish border. On the same day, the Turkish military dispatched troops, armored personnel carriers and missile batteries to the Syrian border. At least one area along Turkey’s border is now controlled by jihadist groups dominated by heavily armed foreign fighters.

July 31, 2012 Syrian rebels said they took control of at least two important police stations in central Aleppo, maintaining their hold on several neighborhoods despite air assaults and shelling by government troops. Residents and activists said the Syrian Army was attacking from a military base on the city’s southern edge, while rebel commanders and activists said the rebels controlled eastern sections of the city as they continued to fight for neighborhoods near the center of the city and in Salaheddiin, a large neighborhood in the southwest part of Aleppo.

Aug. 1, 2012 In rare public remarks apparently designed to marshal government forces seeking to suppress the 17-month revolt, President Bashar al-Assad urged his forces on to show “more readiness and continued preparations” to confront “internal agents” seeking to destabilize his battered country, according to the official SANA news agency. The call to arms was described by analysts as the first public appeal by Mr. Assad since a bombing in mid-July killed some of his most senior aides and spurred speculation about his whereabouts.

Aug. 2, 2012 Kofi Annan, the special envoy of the United Nations and Arab League who has sought unsuccessfully for months to resolve the Syria conflict, submitted his resignation, Secretary General Ban Ki-moon said. Mr. Annan has grown increasingly frustrated over his failure to achieve even a basic cease-fire in the conflict. On the same day of Mr. Annan’s resignation, Syria’s rebels shelled an airport near Aleppo in what was described as one of the first known instances of insurgents using captured heavy weapons, as opposition activists warned that fighting for the city, the country’s main commercial center, would likely intensify. A Syrian activist said Mr. Assad’s army appeared to be preparing for an all-out assault.

Aug. 3, 2012 Armed clashes erupted in at least three Syrian cities amid reports of a deadly mortar attack on a major Palestinian refugee camp in Damascus, an event that threatened to draw Syria’s displaced Palestinian population into its civil war. The new mayhem, reported in Damascus, Aleppo and Hama, came as diplomatic recriminations intensified over the resignation a day earlier of Kofi Annan, the special envoy of the United Nations and Arab League.

Aug. 4, 2012 Explosions and heavy fighting rocked Syria’s two largest cities, Damascus and Aleppo, witnesses and activists said, as the Syrian government and rebel fighters struggled to gain an advantage. Also, Iran’s state news agency reported that unidentified “armed groups” had kidnapped 48 Iranians on the road to the Damascus airport after the Iranians visited a religious shrine.

Aug. 5, 2012 A group of Syrian rebels took responsibility for the kidnapping of 48 Iranians in Damascus a day earlier, but the rebels insisted that their captives were members of Iran’s elite Revolutionary Guards, not religious pilgrims as Iran’s official news agency had reported. Iranian officials said the kidnapped Iranians were pilgrims, denying that any of them were members of the Revolutionary Guards, Iran’s Arabic-language channel Al Alam reported.

Aug. 6, 2012 President Bashar al-Assad fired his prime minister, Riyad Farid Hijab, Syria’s official media reported. But opposition figures said Mr. Hijab had defected to neighboring Jordan along with at least two ministers and three military officers — 10 families in all, opposition leaders said. The announcement of his dismissal came hours after a bomb explosion was reported at the main state television building in Damascus, while fighting raged in Aleppo, Syria’s largest city, and other parts of the country.

Aug. 7, 2012 Thousands of refugees poured out of the embattled city of Aleppo as the military’s fighter jets stepped up bombing raids and rebels said they were struggling to hold some of the city’s neighborhoods while mounting new assaults in others. Activists reported shelling and clashes in at least a dozen areas, adding hundreds of new bodies to a death toll that has already surpassed 21,000. On the same day, Iran moved to reframe the Syrian conflict as part of a wider battle with the United States and other hostile world powers, dispatching the personal representative of its leader, Ayatollah Ali Khamenei, to Damascus for a televised display of solidarity with President Bashar al-Assad.

Aug. 8, 2012 Rebel fighters in Aleppo said that government forces had launched a ground assault, forcing them to pull back from parts of the city because their ammunition was running low, as new disputes arose around the contentious issue of foreign military support for President Bashar al-Assad and for the opposition. Several rebel commanders said shelling and bomb attacks early in the morning had reached new levels of intensity. Residents who had not fled the city reported receiving text messages on their cellphones in the morning asking them to cooperate with the government.

Aug. 9, 2012 Syrian rebels in embattled Aleppo said they made gains in some parts of the city while tactically withdrawing from others as government forces bolstered positions and shelled contested areas on the second day of a ground offensive that the authorities said  inflicted heavy losses on foes of President Bashar al-Assad. As loyalist forces claimed significant advances, Mr. Assad sought to project an appearance of political control and authority, appointing a new prime minister, Wael Nader al-Halqi, to replace Riyad Farid Hijab, who had defected to Jordan several days earlier.

Aug. 10, 2012 In Aleppo, government forces backed by jets, helicopters, artillery and tanks were reported to have resumed their pursuit of rebels, who claimed to be counterattacking in cat-and-mouse fighting after pulling back from the most contested area of the city. The upsurge in violence in recent days sent tens of thousands of Syrians fleeing to neighboring Lebanon, Turkey, Jordan and Iraq. In those countries, the United Nations refugee agency said, a total of more than 146,000 Syrians had registered as refugees, or were in the process of registering, since the fighting began.

Aug. 20, 2012 President Obama threatened military action against Syria if there was evidence that the government of President Bashar al-Assad was moving its stocks of chemical or biological weapons. It was Mr. Obama’s most direct warning of American intervention in Syria.

Aug. 21, 2012 Army shellings and shootings raged in at least three insurgency hot spots across Syria, including what antigovernment activists described as the deadly bombardment of a cemetery in a Damascus suburb during funerals for victims of a freshly discovered massacre. In  Moscow, a Syrian deputy prime minister and the Russian foreign minister rejected warnings by President Obama about possible American military intervention if Damascus were to move or deploy unconventional weapons.

Aug. 22, 2012 Gunfire and shelling rocked Damascus and its suburbs as opponents of President Bashar al-Assad reported a widening campaign by the military to sow fear and death in neighborhoods where the rebels are strong and the government is too weak to fully control.

Aug. 23, 2012 The United Nations said that more than 200,000 refugees had registered in Iraq, Lebanon, Jordan and Turkey, with 30,000 new arrivals tallied in the past week alone. The agency had anticipated a total of 185,000 registered refugees by the end of 2012.

Aug. 26, 2012 Mass burials in Daraya, a Damascus suburb, showed the carnage of the past few days in gruesome detail: scores of bodies lined up on top of each other in long thin graves moist with mud.

Aug. 27, 2012 France’s president urged the Syrian opposition movement to create a provisional government and vowed to extend official recognition once it was formed. Meanwhile, President Mohamed Morsi of Egypt has been staking out a new leadership role by reaching out to Iran and other regional powers in an initiative to halt the escalating violence.

Aug. 28, 2012 The United Nations refugee agency said that the number of Syrian refugees fleeing to Jordan had more than doubled in a week, raising further fears of a growing exodus from Syria that threatens to overwhelm international relief efforts.

Aug. 29, 2012 President Bashar al-Assad said that his government’s battle against rebel forces would need “time” and that a proposal floated by opponents to create buffer zones inside Syria was unrealistic. In an interview that will air on a private Syrian channel, Mr. Assad framed the conflict as a “global and regional war,” praised the heroism of his army and criticized officials in Turkey, who have raised the possibility of military intervention in Syria.

Aug. 30, 2012 At a meeting of the non-aligned movement in Tehran, Egypt’s new Islamist president, Mohamed Morsilikened the uprising in Syria to the revolutions that swept away longtime leaders in North Africa. Ban Ki-moon, the United Nations Secretary General, also denounced the repression of the armed uprising in Syria.

Sept. 1, 2012 Opposition fighters said that they had captured an air defense base in the eastern province of Deir el-Zour, taking at least 16 soldiers captive and seizing weapons and ammunition in what appeared to be part of a broader rebel offensive against Syrian military installations.

Sept. 4, 2012 More than 100,000 Syrians fled their country in August, a sharp acceleration of the exodus prompted by 18 months of conflict, the United Nations said.

Sept. 5, 2012 Iran has resumed shipping military equipment to Syria over Iraqi airspace in a new effort to bolster the embattled government of President Bashar al-Assad of Syria, showing the limits of American influence with Iraq’s Shiite-led government.

Sept. 8, 2012 Clashes between the Syrian military and rebel fighters burst a main pipe that delivered drinking water to thousands of residents of Aleppo, opposition groups said, as the United Nations refugee agency said more than 1.2 million Syrians still inside the country, half of them children, had been displaced from their homes. The agency said the number of people in need of assistance in Syria had doubled since July to 2.5 million, not including the 250,000 refugees who have fled to camps in neighboring countries.

Sept. 9, 2012 The Syrian government accused France of “schizophrenia” for pledging to support a peaceful resolution to the uprising challenging President Bashar al-Assad and aiding the armed groups driving the insurrection. On the same day, an explosion ripped through the northern Syrian city of Aleppo, killing 17 people and wounding 40, the official Syrian state news agency said.

Sept. 17, 2012 With the Syrian conflict reported to be spilling into the Lebanese border area, United Nations investigators said civilians are bearing the brunt of indiscriminate air and ground assaults in the fighting over the future of President Bashar al-Assad. They reported a sharp escalation in government attacks.

Sept. 19, 2012 The bloody civil war in Syria spilled across border areas as rebel forces reportedly drove government troops from a northern frontier crossing in an apparent effort to expand resupply and infiltration routes.

Sept. 20, 2012 At least 30 people, and as many as 100, were killed in the northern Raqqa Province when government warplanes bombed a gasoline station crowded with people, according to activist groups.

Sept. 22, 2012 Commanders of the Free Syrian Army, the main umbrella group for fighters opposing President Bashar al-Assad, said that they had moved their headquarters from Turkey into “liberated areas” inside Syria, in what they portrayed as a major step forward in their efforts to aid, coordinate and control disparate groups of rebels.

Sept. 24, 2012 The raging conflict in Syria will take center stage at the General Assemby of the United Nations in New York, where about 120 world leaders are converging for a weeklong meeting. Despite at least three high-level meetings on Syria, and countless other talks, no broad new initiatives are expected. At the U.N., Lakhdar Brahimi, the newly appointed peace envoy to Syria, told Security Council members that the government of President Bashar al-Assad had no wish to change and that there was no immediate prospect for a diplomatic breakthrough. Mr. Brahimi spoke on a day of fierce Syrian government attacks on the city of Aleppo, with antigovernment activists reporting at least eight people including four children killed by shelling of residential buildings.

Sept. 25, 2012 Several mortar shells launched from Syria landed in the Golan Heights near Israel’s northern border, prompting the Israeli military to file a complaint with United Nations forces operating in the area. No one was injured, and no damage was caused by the shells. Israeli military officials said the firing was aimed at rebel forces holed up in Jubta al-Hashab, a village on the Syrian side of the border.

Sept. 26, 2012 At least two large explosions struck a military headquarters in a busy square in central Damascus, in what appeared to be the second insurgent attack on President Bashar al-Assad’s military in two days. The explosions struck a warren of buildings in one of the capital’s most guarded areas, near a presidential office used by Mr. Assad. In gunfire that followed the attack, a television correspondent from Iran’s English-language satellite network  was killed during a live broadcast.

Sept. 27, 2012 The number of Syrians fleeing to neighboring countries for safety and aid is likely to exceed 700,000 by the end of 2012, according to the United Nations.

Sept. 28, 2012 In response to the unrelenting conflict and recent reports of new massacres in Syria, the United Nations’ human rights body voted in Geneva to strengthen and extend the term of the commission gathering evidence of abuses that could provide a basis for future prosecution by national or international courts. The agency, the United Nations Human Rights Council, voted to continue the work of the Commission of Inquiry for six more months and to increase its financing and its staff members.

Sept. 29, 2012 Fire swept through the old central souk, or marketplace, of Aleppo, damaging a vast and well-preserved labyrinth of medieval storehouses, shops, schools and ornate courtyards as fierce clashes between security forces and insurgents vowing to carry out a “decisive battle” for the city continued. For many residents, the old city, with the souk at its center, is the soul of Aleppo, one of the world’s oldest continuously inhabited cities and Syria’s largest.

Dec. 2, 2012 Syrian warplanes and artillery blasted parts of Damascus and its rebellious suburbs, part of what activists described as intense fighting as rebels tried to push their way into the center of President Bashar Assad’s power base. In central Syria, a car bomb killed at least 15 people, Syria’s official news agency SANA reported. Despite the fighting, merchants around the country closed their shops in an attempt to keep the nonviolent protest movement, called the “Strike of Pride,” alive.

Dec. 6, 2012 Lakhdar Brahimi, the United Nations special envoy to Syria, hosted an unusual three-way meeting with Secretary of State Hillary Rodham Clinton and the Russian foreign minister, Sergey V. Lavrov, to discuss the conflict in Syria. The session, which was held on the margins of a meeting on European security in Dublin, came amid reports of heightened activity at Syria’s chemical weapons sites and signs that Russia may be shifting its position on Syria.

Dec. 7, 2012 Rebels seeking the overthrow of President Bashar al-Assad declared the main airport in Damascus a “fair target,” warning travelers that they used it at their peril. Secretary of State Hillary Rodham Clinton repeated calls for the ouster of President Assad, but said there had been no “great breakthrough” in talks she held in Dublin on Dec. 6 with Russia’s foreign minister, Sergey V. Lavrov, and Lakhdar Brahimi, the United Nations special envoy to Syria.

Dec. 10, 2012 Spillover of the Syrian civil war killed at least 17 people in Northern Lebanon where residents have begun to see themselves as part of the neighboring conflict. In Iran, leaders insist that the conflict in Syria, their main ally in the Arabic world, is manageable and ultimately will be resolved to their advantage.

Dec. 11, 2012 President Obama said that the United States would formally recognize the National Coalition of Syrian Revolutionary and Opposition Forces as that country’s legitimate representative, intensifying the pressure on President Bashar al-Assad to give up his bloody struggle to stay in power. The Obama administration coupled its recognition with the designation hours earlier of a militant Syrian rebel group, Al Nusra Front, as a foreign terrorist organization, affiliated with Al Qaeda.

Dec. 12, 2012 Syrian forces loyal to President Bashar al-Assad have fired Scud missiles at rebel fighters in recent days, in a significant escalation of the conflict. In Morocco, representatives of more than 100 countries and organizations grouped in the so-called Friends of Syria alliance recognized a newly formed coalition of his adversaries.

Dec. 13, 2012 A top Russian diplomat said that Bashar al-Assad’s government is losing control to rebel forces, and said “unfortunately, it is impossible to exclude a victory of the Syrian opposition” — the most clear indication yet that Russia sees Mr. Assad, a longtime strategic ally, as headed for defeat. Also, the United States will send two Patriot missile batteries and about 400 military personnel to Turkey to defend against a possible Syrian missile attack, two allied officials said.