During the First World War, the Italian Expeditionary Force (IEF) was a joint Franco-British military force sent to Italy in October 1917.
Following the Battle of Caporetto (24 October to 19 November 1917), the Italian Front collapsed. In order to ensure this did not lead to Italy withdrawing from the war the allies organised the Italian Expeditionary Force to reinforce the Italians. Even as the battle unfolded, General Luigi Cadorna invoked the agreement reached at the Chantilly conference of December 1915. There the allies had agreed that should any of the allies come under threat, the other allies would support them. The first French troops arrived on 27 October 1917. The first British troops followed them after a few days.
The IEF consisted primarily of the French Tenth Army with the addition of the 12th Army Corps. They took up station around Verona.
The British Expeditionary Force (Italy) came under the command of General Herbert Plumer. The principal units in the BEF(I) were the 23rd, 41st, 7th, 48th and 5th Divisions. However the 5th Division returned to France on 1 March 1918, followed by the 41st Division in April.