Officially, American infantry are discouraged from riding into battle on tanks. This was a popular mode of transportation during World War II, and after that conflict, Soviet tanks continued to have hand holds welded to the turret so more infantry could ride along. Post World War II tanks did not have such hand holds. When the U.S. put the M-1 Abrams tank into service, it warned tank crews, and infantry, that the M-1 could move a lot faster (because of a more powerful engine) and over rougher terrain (because of a better suspension system) and would be more likely to throw embarked infantry off the tank. But the training manuals still allowed for infantry on the tanks, and in Iraq, non-motorized infantry, from units like the 101st Airborne division, were often seen riding around on M-1 tanks, and quickly dismounting when the tank came under fire. This is part of the drill for riding on a tank, getting off quickly when the enemy starts shooting at you. The tank commander wants to move his turret around to fire at the enemy, and he can't do that with infantry hanging on to the turret. This points out another downside of riding on a tank. Jumping off looks fine in theory, but it's over five feet to the ground, and with all the ammo and other stuff the infantry are carrying, hitting the ground is hell on the knees and back. Many tank crewmen find out years later when their knees and backs develop problems from all those instances when they just jumped off their tanks.