An errant attack by US warplanes in Deir ez-Zor on Sept. 17 that killed 62 Syrian soldiers marked the beginning of the end of a short-lived US-Russia agreement to provide humanitarian relief to Syrians, jump-start political talks and coordinate targeting against terrorist groups.

Russian Foreign Minister Sergey Lavrov said that he found it “very hard to believe” that the United States could make such a mistake in Deir ez-Zor, where Syrian forces were battling Islamic State (IS) militants, adding that he had, however, conveyed an apology on behalf of the United States to Syrian President Bashar al-Assad.

On Sept. 19, two days after the Deir ez-Zor incident, a statement by the Syrian General Command of the Army and Armed Forces declared an end to the truce. The United States blamed Russia for a deadly attack on a United Nations aid convoy that night in Aleppo that killed 12. UN Emergency Relief Coordinator Stephen O’Brien, while not accusing Russia, said that if the attack on the convoy was deliberate it would constitute a war crime.

On Sept. 22, Syrian military forces, backed by Russia and Iran, unleashed a furious assault to retake those areas of Aleppo primarily held by Jabhat Fatah al-Sham (Conquest of Syria Front), previously known as Jabhat al-Nusra, al-Qaeda’s Syria affiliate, and aligned groups including Ahrar al-Sham.