How many people were in the British Expeditionary Force?

The British Expeditionary Force (BEF) was initially established in 1907 and became notably active during World War I. At the start of the war in 1914, the BEF consisted of approximately 120,000 troops, which later expanded to over a million soldiers throughout the conflict. The force played a crucial role in the early battles of the war, particularly during the Retreat from Mons and the First Battle of Ypres.