On 24 October 1917 the Austrians and Germans launched the Battle of Caporetto (Italian name for Kobarid). Chlorine-arsenic agent and diphosgene gas shells were fired as part of a huge artillery barrage, followed by infantry using infiltration tactics, bypassing enemy strong points and attacking on the Italian rear. At the end of the first day, the Italians had retreated 19 kilometres (12 miles) to the Tagliamento River.