Out of 50 tanks sent to attack the Somme, only 36 made it. The rest broke down and/or got stuck in the mud, with horrendous results. WWI's Siege of Fray Bentos at Passchendaele, a very fancy name for what ultimately boils down to "a protracted assault against a tank that got stuck in the mud," is a perfect example of this. Cheekily named after a tinned meat company, the Fray Bentos was chugging along until it fell into a crater and couldn't get out again. One gun was pointing at the sky, the other at the ground -- and to make matters worse, the Germans had noticed.
via The Telegraph
They do have an infuriating attention to detail.
For three days, the men of the Fray Bentos found out just how shitty being in a tank could be. Any attempts to get out were met with death and grievous injuries, and escape was made almost impossible after the corpse of one of the crew wedged the door shut. The temperature inside rose to about 90 degrees fahrenheit. The breach of one of the main guns crushed a man's ribs and left him to die slowly. German forces made several attempts to swarm the tank with grenades and had to be repelled. On the third night, when water and rations had been exhausted and those still alive were low on ammo, they decided to mount a suicidal escape. But the Germans were only interested in capturing the tank and so let the Fray Bentos survivors leave in peace. That's how much WWI tanks sucked -- even the enemy didn't have the heart to shoot you once you finally managed to escape one.
Things did improve for tank crews in WWII, but not a lot. It was still an insanely miserable, dangerous, flammable place to fight a war. And mud was still a problem.
"Aw shit, I knew we forgot about something."
The makeup of the most common Allied tank, the Sherman, was riddled with so many small weaknesses it might as well have been a miniboss in a video game. If hit low, the interior was liable to erupt into a ball of hellfire, roasting everyone inside. That's the opposite of how a tank is supposed to work. In WWII, the loss rate of Allied Sherman tanks was a blood-pressure-ramping 580 percent. They malfunctioned, caught fire constantly, and were basically horrible death traps for those inside. In fact, one of the reasons the Allies achieved armor superiority over the Germans is that they had so many bullshit Sherman tanks they were forced to continuously improve them. So don't listen to the movies -- you were as likely to die from merely occupying a tank as you were from being shot by one.