In the early stages of the First World War Peniķis served as a company commander in Galicia and in battles around Krakov. He was wounded in December 1914. In 1915 he was promoted to the rank of colonel and participated in battles in Belorussia. In autumn of 1916 he was transferred to the Latvian Rifleman units and became commander of 2nd Riga Latvian Rifleman Regiment. He led his regiment in the Christmas Battles and at the Battle of Jugla in autumn of 1917. After the October Revolution, Peniķis left the army and stayed in German-occupied Vidzeme, where he was interned. He was released in November 1918.