Twice in the 20th century, a British Expeditionary Force has taken the field in Northern France to fight beside the French Army at the outbreak of a European War. Twice, by something approaching a miracle, the Expeditionary Force has survived initial disaster and the threat of complete destruction. But the differences between the Retreat to Dunkirk in 1940 and the first encounter with the enemy at Mons in 1914 are significant. In 1940, the Retreat to Dunkirk led to the fall of France and it took four more years of war before the British Army could avenge its defeat. In 1914, an interval of only two weeks separated the first encounter with the enemy at Mons on Sunday, August 23rd, from the counter-stroke when Joffre struck back across the Marne on Sunday, September 6th. This action proved to be one of the most decisive battles of history leading to the complete collapse of the German War Plan.