In 1942 the US Army issued an order to build a half-track that would be distributed among the Allies Forces through the lend-lease program. The chassis and mechanical components came from the M-5 half-track vehicle and some parts of the previous M-2 model were added, giving rise to the new M-9 half-track model. Great part of the M-9 vehicles were destined to the British Army, although the Soviet Union purchased more than 400 units directly from the United States. In 1943 the M-9A1 variant appeared, with a new circular assembly and 3 pintle mounts for machine guns among other new arrangements. Some 3,500 M-9 and M-9A1 half-tracks were built, serving in more than a dozen countries. The excellence of this design is demonstrated by the fact that they have been in service until the 1990s in some armies of the Middle East.
M-9A1 half track gallery and more info