USARPAC is a ready, responsive and indispensable member of the joint force team under the Combatant Commander, U.S. Pacific Command (USPACOM). USARPAC provides combat-ready forces in support of security operations—from theater security cooperation to warfighting—to promote regional stability and ensure successful crisis response or decisive victory.

Major USARPAC units include: the 25th Infantry Division; 8th Theater Sustainment Command; 311th Theater Network Command; 94th Army Air Missile Defense Command; 9th Regional Readiness Command; and 196th Infantry Brigade. Also, U.S. Army Installation Management Command, Pacific, which oversees U.S. Army, Alaska; U.S. Army, Japan; and U.S. Army Garrison, Hawaii, is headquartered at Fort Shafter, which is also home to USARPAC. The Light Fighters of the 25th ID, "Tropic Lightning" Division, are capable of deploying to a theater of operations anywhere in the world to conduct missions across the spectrum of warfare and perform combat and non-combat operations.

As the strategic reserve for the United States Pacific Command (PACOM), the 25th ID has a standing mission to deploy when directed and conduct operations on arrival.

The 25th ID is a tactical force with strategic responsiveness and flexibility. It operates as a combined arms force with organic or attached/ OPCON, or supporting infantry, armor, engineers, artillery, aviation and air defense.

Originally constituted in Korea in 1968 as the 8th Field Army Support Command, the 8th TSC, a centralized logistics organization, was last reorganized Jan. 11, 2006, as the 8th TSC (Provisional) from the inactivated 45th Corps Support Group. The following units constitute the 8th TSC: the 8th Special Troops Battalion, 29th Engineer Battalion (Topographical), 84th Engineer Battalion (Heavy), 125th Finance Battalion, 8th Human Resources Sustainment Center, 8th Military Police Brigade, 10th Area Support Group and the 45th Sustainment Brigade.