France, following the great casualties of the Great War in 1914-1918, had suffered a significant decline in birth rates and as such by the time of the Second World War, its armies were severely undermanned. Furthermore, the economy of France had since not yet recovered and its industries were half their former size.
Riots and attempted political takeovers all worsened the state of the nation. However, collapse was never seen to be a possibility and overall, the condition of France was better than that of other nations which had suffered a larger toll from the war.
World War II
Both France and Britain declared war on Germany after the invasion of Poland, with British troops landing in France to defend against an German invasion of France. France reinforced and secured the Maginot Line, but left the border with Belgium relatively undefended.
On 10 May, 1940, Germany circumvented the Maginot Line by invading Belgium, and in six weeks conquered all of France using Blitzkrieg tactics. The forced the British off the Continent, and the French government into exile in Africa. This exiled government would become Free France.