Two suicide bombings hit Damascus on Wednesday, including an attack at a central courthouse that killed at least 32 people. The second wave of deadly attacks in the capital in less than a week after twin bombings killed 74 on Saturday.
Although several hundred US special forces troops have been active in Syria for months now, the Marines' arrival marks the largest deployment of America's conventional forces in Syria since the civil war began six years ago.
Iraqi forces on Sunday launched an operation to retake the west bank of Mosul, the latest phase of a massive offensive on the ISIS bastion. Here are the main dates concerning the Islamic State group in Iraq and Syria.