The United States Army and Marine Corps began arriving in France in 1917 following the nation's declaration of war against Germany in April of the same year. The army formed the largest body of troops and consisted of three different organizations: eight Regular Army divisions, seventeen National Guard divisions and eighteen National Army divisions, formed by men drafted for national service.
Most of 1917 was spent training the troops in the US, transporting them to Europe, further training by our French and British allies and then taking over sections of the allied trench line as the units became ready for front line service.
The timeline below lists the major operations that the Americans participated in. It begins in late 1917 and early 1918 with small supportive roles to the British Army. By the late spring and summer, as the number of American units increased and were ready for combat, they fought with the French Army in defensive battles that ended the series of German attacks begun in March 1918 that were intended to defeat the allies.
American participation in the Champagne-Marne Operation, July 15-18, 1918, is an example and is significant because it stopped the final German attack, put them on the defensive and marks the first allied attack that began the campaign that forced the them out of France and Flanders and for them to ask for an armistice in November 1918. American troops continued to serve with British and French armies up until the end of the war as shown in the list of operations. However, as the US Army grew in size and experience it began to undertake its own major offensives such as the September 12-16, 1918 St. Mihiel Operation and the September 26-November 11, 1918 Meuse-Argonne Offensive. Each of these and the months of manning sections of the allied defensive line produced the casualties that Base Hospital 28 and other American Medical Department units were created to treat. Therefore, where data is available the numbers of casualties resulting from these specific periods of intense fighting are provided.
However, these statistics do not convey the entire picture of what the Medical Department faced in terms of the numbers of men they would treat. For example, the September 12-16, 1918 St. Mihiel Operation resulted in 8,600 casualties, but in this sector between January 8-September 11 and September 17-November 11, 1918 there were 18,695 casualties in addition to the 8,600.
By the end of the war the American Army suffered 52, 947 killed and 202, 628 wounded.
November 20-December 4, 1917-The Battle of Cambrai: three regiments of US Army engineers are attached to support the British 3rd Army's attack at Cambrai. Casualties: 77
March 21-April 6, 1918-The Somme Defense: three regiments of US Army engineers and four aero squadrons are attached to support the British 5th Army's defense against the German Army's ‘Michael Offensive' in northern France.
April 9-27, 1918-The Lys Operation: three regiments of US Army engineers and one pursuit squadron are attached to support the British Army's defense against the German's ‘Georgette Offensive' in Flanders.
May 27-June 5, 1918-The Aisne Defensive Operation: the American 2nd Infantry Division, 2nd Field Artillery Brigade, 4th Marine Brigade and smaller units were attached to the French Army for the defense against the German Army's 'Blucher-Yorck Offensive'.
May 28-31, 1918-The Battle of Cantigny: the American 1st Infantry Division contributes to the French counter-attack resulting in the capture of Cantigny. Casualties: 5,163
June 3-June 4, 1918-The Battle of Chateau-Thierry: the American 2nd Infantry Division and 2nd field Artillery Brigade support the French counter-attack that captures Chateau-Thierry. Casualties: 1,908
June 6-26, 1918-The Battle of Belleau Wood: the American 7th Infantry Regiment, 4th Marine Brigade and the engineers of the 2nd and 3rd Infantry Divisions support the French Army by their successful capture and defense of Belleau Wood. Casualties: 8,400
June 9-June 13, 1918-The Battle of Montdidier-Noyon: the American 1st Infantry Division contributes to the French counter-attack by their capture of Montdidier-Noyon.
June 26-July 3, 1918-The Battle of Vaux: the American 2nd Infantry Division support the French counter-attack with the capture of Vaux. Casualties: 7,588
July 15-18, 1918-The Champagne-Marne Operation: the American 26th, 3rd, 28th and 42nd Infantry Divisions and the 369th Infantry Regiment with the French 6th, 5th and 4th Armies successfully defend against the German 'Friedenstrum Offensive' and launch a counter-attack on July 18th. Casualties: 7,317
July 18-August 6, 1918-The Aisne-Marne Operation: the American 1st, 2nd, 26th, 3rd, 28th, 4th, 42nd and 32nd Infantry Divisions are organized into the American I and III Corps that participate with the French 10th, 6th, 9th and 5th armies in the Franco-American offensive that marks the beginning of the German Army's retreat from France. Casualties: 38,490
August 7-November 11, 1918-The Oisne-Aisne Operation: the American III Corps Headquarters, corps troops, 28th, 32nd, 77th Infantry Divisions and the 370th Infantry Regiment are attached to the French 10th, 6th and 5th armies and contribute to the French counter-attacks over four months that cause the Germans to retreat and to ask for an armistice. Casualties: 2,767
August 19-November 11, 1918-The Ypres-Lys Operation: the American 27th, 30th, 37th and 91st Infantry Divisions are attached to the Belgian, French 6th and British 2nd armies in support of the allied offensives in Flanders that forced the retirement of the German Army from Flanders. Casualties: 2,043
October 24-November 4, 1918-The Vittorio Veneto: the American 332nd Infantry Regiment, 331st Field Hospital and a motor truck train are attached to the British 31st Division in support of the allied counter-attack against the Austro-Hungarian Army in northern Italy.
August 8-November 11, 1918-The Somme Offensive: the American 27th, 30th, 33rd, 78th and 80th Infantry Divisions are organized as the American II Corps and fought with the British 4th Army in eight engagements in Belgium and in northern France at the Battles of Bellicourt, Montbrehain and the Selle River. Casualties: 15,034
September 12-16, 1918-The St. Mihiel Operation: the American First Army that consisted of the American I, IV and V Corps with the support of the French II Colonial Corps successfully reduced the St Mihiel salient by attacking and forcing the German Army to retreat from the Salient. Casualties: 8,600
September 26-November 11, 1918-The Meuse-Argonne Offensive: the American First Army that consisted of the American I, III, IV and V Corps with the support of the French Fourth Army launches its largest operation that led to the retreat of the German Army and their asking for an armistice ending American operations and the war. Casualties: 110,508
American Armies and Battlefields in Europe, Center of Military History United States Army (Washington, D. C. 1995)
Coffman, Edward M, The War to End All Wars The American Military Experience in World War I (Madison, 1986)
Photographic images: National World War I Museum at Liberty Memorial
United States Army In The World War 1917-1919, Military Operations of the American Expeditionary Forces, Volume 1, Center of Military History United States Army (Washington, D. C. 1988)
United States Army In The World War 1917-1919, Military Operations of the American Expeditionary Forces, Volumes 4-9, Center of Military History United States Army (Washington, D. C. 1989)