expelled the Serbian troops by force. Bulgarian sources on the other hand, outline several Serbian intrusions into Bulgarian territory as the start of hostilities. Bulgarian troops were positioned away from the border in order to not give Serbia cause for attack by defending the border by force. After several incursions fire was finally exchanged on the . 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. No territorial changes were made to either country, but the Bulgarian Unification was recognised by the Great Powers. However, the relationship of trust and friendship between Serbia and Bulgaria, which had been built during their long common fight against Ottoman rule, suffered irreparable damage. Serbian army The Serbian army's infantry weaponry stood up to the most modern standards of the time (Mauser-Milovanović single fire rifles with excellent ballistic characteristics). However, the artillery was ill-equipped, still using muzzle-loading cannons of the La Hitte system. Breech-loading cannons of the De Bange system had been ordered and paid for, but did not arrive in Serbia until 1886. The total number of Serbian armed forces expected to take part in the military operation was about 60,000. King Milan I divided his force into two armies, the Nishava and Timok armies. The first undertook the main objective, i.e. to overcome the Bulgarian defences along the west border, to conquer Sofia and advance towards the Ihtiman heights. It was there that the army was supposed to encounter and crush the Bulgarian forces coming from the southeast. Serbia's main advantages on paper were the better small arms and the highly educated commanders and soldiers, who had gained a great deal of experience from the last two wars against the Ottoman Empire. However, internal Serbian problems supplemented by king Milan's conduct of the war, nullified most of these advantages: In order to claim all the glory for the victory he considered imminent, King Milan did not call