Shortly after the end of the First Balkan war the Bulgarian Army was ordered to engage in a much shorter but an even costlier conflict that was the Second Balkan war. The 4th division, including the 8th Regiment, was now part of the Bulgarian Fourth Army which was facing the Serbians in Vardar Macedonia. Following the unsuccessful Bulgarian attack in the Battle of Bregalnica the 4th Army retired on positions around the village of Kalimantsi. On 24 June Colonel Kiselov was assigned commander of the 7th Division's rearguard which was occupying the defensive line. Here he managed to convince his superiors not to abandon the positions and instead resist the advancing Serbians. This act allowed the 2nd Bulgarian Division to safely withdraw to its new line and ensured Bulgarian success in the Battle of Kalimantsi. Nevertheless, Bulgaria was forced to ask its enemies for peace and the Second Balkan War officially ended with the humiliating Treaty of Bucharest.