Adolf Hitler wasn't always a malicious dictator with a taste for power. In his youth, he was a very artistic young man who wanted nothing more than to attend art school. He did have dabbling in German nationalism, even though he was born in Austria, but those didn't come out until much later. He attempted to attend art school but since he had dropped out of his schooling at age 16 he didn’t have the certificate needed to get into a college program. He moved to Munich in 1913, with the goal of avoiding service in the Austro-Hungarian army. However, they found him and returned him for his physical examination to serve.
Hitler ended up failing his physical for being 'too weak' and went back to Germany. As World War I geared up, Hitler enlisted in the German army. Standards were much lower as soldiers were in high demand, so he managed to avoid the physical exam rejection he had experienced in Austria. He served dutifully, proud to be a member. He was involved in many major battles and wounded twice during his time in the war. He was also awarded many medals for his service.
Hitler's anti-Semitic views continued to develop during his time in the army, but he was totally committed to Germany, thanks to his nationalist views that he'd long held about the country. He served his country well until the end of World War I, which is when his mind started to change. As Germany surrendered at the end of the war, Hitler felt his country had been 'backstabbed', or betrayed by its leaders. He saw it as a coward's move, and made a mental note of how it made him feel. He continued his army service and during an infiltration of the German Workers Party, he actually decided to join the party in 1919.
After Hitler joined the German Workers' Party, he quickly became a leader and renamed the group the Nazi Party (National Socialist German Workers Party). This ended his loyalty to Germany and fueled his anti-Semitic views, taking him from a decorated war hero to a dictator in a matter of just over a decade. He felt that the Jews were the problem of Germany, and that if it were to ever be the world power he dreamed it to be as a young boy, they needed to be eliminated. This was partly influenced by his existing views, as well as new perspectives he gained as a part of the Nazi party. Either way, The Adolf Hitler that served in World War I became a changed man very quickly.