The HMMWV is a four-wheel drive military automobile that appears in Spec Ops: The Line. "HMMWV" is an acronym meaning "High Mobility Multipurpose Wheeled Vehicle", but the vehicle is commonly known as a "Humvee".
These vehicles, along with Strykers, were the 33rd Infantry's primary means of moving men before the disaster. After the sandstorms, some vehicles were lost to the elements or eventually broke down due to lack of parts. Some disabled Humvees were used as machine gun bunkers.
One 33rd soldier can be heard ordering his men to help him scrap a Stryker for metal to jury-rig extra armor on their Humvees, so it is assumed the vehicles were inadequately protected during the 33rd's own civil war and during the insurgent attacks. This is unusual, because at the time of the game's release, up-armored Humvees were common in the US military.
The 33rd had a small number remaining by the time Walker and his team arrived in Dubai. Several were stationed at the gate and were destroyed during Delta Squad's attack. Numerous Humvees protected the 33rd's water supply and attempted to chase down and recover the water after it was stolen by the CIA.
After the destruction of the radio tower, several squads drove to the crash site of Delta Squad's stolen Black Hawk in Humvees. The 33rd's last remaining Humvees were destroyed during the final battle at the Gate.
Not all the Humvees in Dubai were destroyed however, as Delta Squad passed many abandoned Humvees through out the game. At the game's end, regardless of what ending Walker chooses, it is likely these remaining Humvees will just remain as static reminders of how the city was destroyed.
A number of them are also seen in the epilogue being driven by Falcon One. Unlike the 33rd's Humvees, these were painted in woodland camouflage.