1st Battalion 9th Marines

The 1st Battalion 9th Marines (1/9) is an infantry battalion of the United States Marine Corps. Formed during World War I, it served until the mid-1990s when it was deactivated to make room for one of three light armor reconnaissance battalions. During the Vietnam War, 1/9 sustained the highest casualty rate in Marine Corps history.

In late 2005, the battalion was once again activated and attached to the 8th Marine Regiment at MCB Camp Lejeune. Although the first full company has deployed, 1/9 was not expected to be ready for deployment as a battalion until May 2008. On 19 April 2007, 1/9 was officially stood up with all of its subordinate units fully manned.