Although operational testing was still underway, as a consequence of the United States' military involvement in South Vietnam, the C-141 was quickly dispatched to the region to commence operational sorties with the combat zone. The type became heavily used throughout the latter stages of the Vietnam War, its transport capabilities being in high demand. Even following the arrival of large numbers of C-141s in the Vietnam theatre, the type was never able to fully replace the C-124 Globemaster II due to its inability to transport outsize equipment in-theatre; this situation was later addressed by the introduction of the even larger C-5 Galaxy. The final duties performed by the C-141 in the conflict were repatriation flights, bringing home thousands of American prisoners of war (POWs).