Bulgarian 1st Occupation Corps

The Bulgarian Army had not participated in the Invasion of Yugoslavia, but had agreed to take over occupational tasks to free German combat troops.

The Fifth Army did not actually enter beyond Serbian borders before the Balkan War, except for part of Pirot, which was considered a traditional Bulgarian region.

In response to the German requirements for Bulgarian occupation in Serbia itself, at the suggestion of the General Staff, the First Occupation Corps was formed under the command of Lieutenant General Asen Nikolov and Chief of Staff Colonel Stoyko Ivanov.

In October 1942, several battalions of the 9th Pleven Infantry Division participated in Operation Kopaonik against Mihailović's Chetniks.

The rest of the personnel withdrew to the old borders of Bulgaria, abandoning some of their equipment and heavy weapons during the retreat.