 Complete the following phrase:  At the outbreak of World War I he was the nominal supreme commander of the Serbian army; true command was in the hands of the Chief of Staff of Supreme Headquarters, a position held by Stepa Stepanović during the mobilisation, Radomir Putnik 19141915, Petar Bojović 19161917 and Živojin Mišić 1918. The Serbian army distinguished itself in the battles at 