After the accession of Bulgaria in the First World War, he commanded the 2nd Army. He led the operations in Macedonia which ended with the defeat of the Serbs in the Battle of Ovche Pole. With that success, the Bulgarians did not allow the meeting of the Serbian Army and the Anglo-French forces who embarked in Solun. In February 1917, he was in command of the 3rd Army and defeated the Romanians in Dobrudzha. From 8 September 1918, he became commander-in-chief of the Bulgarian Army after the illness of General Nikola Zhekov. He participated in the Battle of Dobro Pole, which was the crucial Serbian victory in 1918. He was dismissed in 1919.