"Viribus Unitis", along with her sister ships , and the remainder of the Austro-Hungarian Navy, was mobilized on the eve of World War I to support the flight of and . The two German ships were stationed in the Mediterranean and were attempting to break out of the strait of Messina, which was surrounded by enemy troops and vessels and make their way to Turkey. After the Germans successfully broke out of Messina, the navy was recalled. The fleet had by that time advanced as far south as Brindisi in south eastern Italy. "Viribus Unitis" also participated in the bombardment of the Italian city of Ancona in May 1915. Following these operations "Viribus Unitis" remained in Pola for most of the remainder of the war.