On April 7, 2017 (Syria local time) the United States Navy launched 59 Tomahawk Land Attack Missiles (TLAMs) into positions in Syria. Striking the Syrian Air Force Shayrat airbase that was known to house chemical weapons. The airbase was home to the Syrian Air Force 50th Air Brigade who had oversight of the 675th Fighter Squadron, 677th Fighter Squadron, and 685th Fighter Squadron. The Syrian fighter jets stationed at Shayrat airbase were mostly MiG-23 and SU-22 Russian fighter jets. The missile attack targeted Syrian Air Force aircraft, hardened aircraft shelters, petroleum and logistical storage, ammunition supply bunkers, air defense systems, and radars.
The Pentagon did warn the Russian military of the upcoming attack. It is a given that the Russians would warn the Syrian government and relocate MiG fighter jets and other equipment to a safer location. After the US attacked the airbase, it was reopened the next day as videos were being published on social media.
The damage to the airfield was minimal and no heavy damage to the airfield. You can verify this by US Department of Defense published pictures of the air strike. There was severe damage to the perimeter of the airfield. The US missile attack was in response to the chemical weapons attack on April 4 that killed over 80 men, woman, and children.
The Russian military shut down the communication line with the United States Pentagon. The communication line (deconfliction channel) was set up jointly by the United States and Russian military. The line is to prevent accidents or any type of confrontation between the two countries.
11th Marine Expeditionary Unit in Syria
On March 9th the Washington Post reported that elements of the U.S. Marine Corps artillery unit have been deployed to Syria. They will support US Forces and local forces according to the article. There is no mention exactly what do they mean when they say local forces to fight the terrorists.