Churchill delivered “Their Finest Hour” under challenging circumstances: The majority of Europe had fallen under Nazi power, culminating in the defeat of France, Britain’s closest ally at the time. The war in France was fought between the German army, which had recently invaded Belgium and the Netherlands, and the Allied forces of France, Britain, and Belgium. The German strategy involved a massive assault through the Ardennes Forest, a heavily wooded and hilly region that was thought to be impassable to tanks. However, the German army was able to push through this area and quickly advanced toward Paris, causing the French forces to retreat and ultimately leading to the fall of France. The campaign was marked by several key battles, including the Battle of Sedan, the Battle of Arras, and the Battle of Dunkirk, collectively called the “Battle of France.” The conquest was a significant victory for Germany and solidified Nazi control over much of Western Europe. It also had major consequences for the Allied forces and led to the resignation and subsequent arrest of the French prime minister (Paul Reynaud, who opposed signing any armistice with Nazi Germany). For Churchill, who became the British prime minister in May 1940 after Neville Chamberlain resigned following the Nazi invasion of Norway, the invasion of France was the first major test of leadership.