Background Monarchy and the constitution Belgium gained its independence from the United Netherlands in 1830 and was established as a popular and constitutional monarchy under a bicameral parliamentary democracy. A liberal Constitution was written in 1831 which codified the responsibilities and restrictions imposed on the monarch. Although the King, as head of state, was prevented from acting without the approval of a government minister, he was allowed full control of military matters in his capacity as Commander-in-Chief. Which responsibility would take precedence if they became incompatible was left ambiguous and this uncertainty would lie at the heart of the royal question. The first king, Leopold I, accepted the terms of the Constitution but attempted to use its ambiguities to subtly increase his own powers. This was continued by his successors, although with little real success. King Leopold III Leopold III came to the throne in 1934 after his father, Albert I, died in a mountaineering accident. Albert, known as the "Knight King" (roi-chevalier or koning-ridder), had been hugely popular in Belgium after commanding the Belgian army during World War I (1914–18) while much of the country was under German occupation. Leopold's reign was marked by economic crisis in the wake of the Great Depression, and political agitation by both far-left and far-right parties. Amid this period of crisis, Leopold attempted to expand the powers of the monarch. He was widely suspected of holding authoritarian and right-wing political views. From 1936, Leopold was a strong supporter of Belgium's "independence policy" of political neutrality in the face of Nazi Germany's increasingly aggressive territorial expansion. German invasion and occupation, 1940–44 On 10 May 1940, German forces invaded neutral Belgium without a formal declaration of war. Leopold headed immediately to Fort Breendonk, the headquarters of the Belgian army near Mechelen, to take control of the army. He refused to address the Belgian parliament beforehand, as Albert I had famously done at the outbreak of World War I. The speed of the German advance, using the new Blitzkrieg approach, soon pushed the Belgian army westwards despite British and French support. On 16 May, the Belgian government left Brussels. Break between King and Government Soon after the outbreak of war, the King and Government began to disagree. While the Government argued that the German invasion had violated Belgian neutrality and made Belgium one of the Allies, Leopold argued that Belgium was still a neutral country and