The fuel needs of the U.S. Army in combat zones has grown so much in the last two decades, that, for the first time since World War II, the ground forces are consuming more supplies (in terms of tons) than the air force. Supply requirements for modern war are considerable. For example, it requires more than a hundred pounds of supplies per soldier per day to keep the troops in action. The 1991 Gulf War required the movement of seven million tons of stuff to supply half a million troops for six months. Most of that was for fuel, and most of it was used by the air force.
Military aircraft have enormous appetites for fuel. Each B-52 flying off from its base carries over 140 tons of jet fuel, each F-15, over five tons. KC-135 tankers fly off with nearly a hundred tons of fuel on board. But the army is using more fuel to generate electricity (for electronics, and air conditioning to keep the delicate gear, and the troops that tend to it, from overheating). That means that the army has been demanding more fuel. Meanwhile, the air force has been using less. That's because of smart bombs, which get the target destroyed using far fewer bombs. That requires fewer bombers in the air. So now, the army is using most of the supplies coming into the combat zone.