As it happened, the Ottomans did not intervene, and the Serbian army's advance was stopped after the Battle of Slivnitsa. The main body of the Bulgarian army traveled from the Ottoman border in the southeast to the Serbian border in the northwest to defend the capital Sofia. After the defensive battles at Slivnitsa and Vidin (the latter's defence was organized by Atanas Uzunov), Bulgaria began an offensive which took the city of Pirot. Austria-Hungary then stepped in and threatened to join the war on Serbia's side if the Bulgarian troops did not pull back.