🌍 Why World War II Happened — Explained Simply World War II began because a mix of political anger, economic problems, and aggressive dictators pushed the world into conflict. After World War I, Germany was punished heavily, losing land, money, and military power. This created deep resentment. Adolf Hitler used this anger to rise to power, promising to rebuild Germany. Meanwhile, countries like Italy and Japan also wanted more land and power. When Germany invaded Poland in 1939, after already t