The new Mobile Protected Firepower vehicle will require its developers to carefully balance competing demands. If the tank is too thickly armored or heavily armed, it could be too heavy for the Air Force’s planes.

If it’s too thinly armored or under-armed, it might not survive in combat a well-equipped foe. The Chinese army has begun fielding its own high-tech light tank. Russian forces have operated air-mobile armored vehicles for decades.

But if recent history is any indication, the biggest obstacle the Army faces in developing the new tank is… the Army itself. The branch has tried several times in recent years to buy new armored fighting vehicles. Almost every new vehicle ended up overweight, over-budget—and canceled.