He had a Profound Affinity For Tanks, But He was Horrible at Driving One.
However, even though Arnold had an early interest in working out and building muscle, he chose acting as his first career path. He enlisted in the Austrian military as soon as he was old enough to do so, and served for a while before making his mark on the circuit. Because he was born in 1947, he was exposed to the military as a child and grew up in the post-WWII era.
He made the decision to enlist at the time he did due to his growing interest in tanks. It was unfortunate that even though he had passed the tank exam, he was not the best driver. When Arnold drove into the garage wall by mistake, it collapsed, allowing the gas and water pipes inside to escape. While Arnold was driving into the garage, this happened.