Book excerpt: Includes The Americans in the First World War Illustration Pack - 57 photos/illustrations and 10 maps The analysis of the impact of the American Expeditionary Force (AEF) in the Great War has fallen into two competing camps. The first believes that the AEF was the war winning factor in coalition warfare. The opposite view holds that the AEF itself had no true impact, but rather it was the industrial might and the manpower potential of the United States (US) that was the key element to victory. The caveat to both views was that the AEF did not have enough time in combat to truly show its martial ability. This thesis attempts to analyze the combat effectiveness of the AEF by comparing its experience with that of the British Expeditionary Force (BEF) in 1916. The rate of change in the ability of the AEF to adapt to modern warfare will be shown to be slightly higher than that of the BEF of 1916. By November 1918, the AEF was not completely tactically combat effective, but it had dramatically improved from where it started and clearly demonstrated the potential to continue to improve at the same pace.