According to academic Paul Mojzes: "it appears that ethnic cleansing (at a minimum) and genocide (at the maximum) did take place between 1915 and 1918",[1] what historian Alan Kramer has termed a: "dynamic of destruction".

[2] The occupation ended in late September 1918, after the Allied offensive at Dobro Polje, spearheaded by Serbian and French forces, pierced the Bulgarian front and liberated Serbia.

[8] Bulgaria's traditional aims lay in the Bulgarian-inhabited areas of Macedonia, Dobrudja, and European Turkey, but in 1915 it demanded territory well beyond its ethnographic borders.

[10] On 6 October 1915 under the overall command of German General August von Mackensen, Austria-Hungary and Germany began the fourth invasion of Serbia since the beginning of the war.

Bulgaria entered the war on the side of the Central Powers, with the primary goal of regaining territory briefly gained from the Ottoman Empire in 1912–13, then lost to Serbia in 1913.

The pressure of Austro-Hungarian, Bulgarian and German armies in the north, and their massive superiority in numbers and equipment, forced the Serbs to withdraw across northern and central Albania.

[14] Two administrative zones supervised by a military commander were created: Bulgarian policy in Macedonia, and to some degree in occupied Serbia, was motivated by what historian Alan Kramer has termed a 'dynamic of destruction' a desire not just to defeat the enemy militarily, but also to erase all traces of its culture and destroy any evidence that it had ever been there at all.

[2] About half of Vardar Macedonia, as the region was called by Serbia, was also inhabited by various ethnic groups who did not identify as Bulgarian; according to a 1912 survey by the British Foreign Office, namely Serbs, Turks, Albanians, Greeks, Vlachs,[b] Jews and Gypsies.

[30] The Documents relatifs aux violations des Conventions de La Haye et du Droit international, commis de 1915–1918 par les Bulgares en Serbie occupée, a report covering alleged atrocities committed in Serbia, published after the war, stated that ‘anyone unwilling to submit him or herself to the occupiers and become Bulgarian was tortured, raped, interned, and killed in particularly gruesome manners, some of which recorded photographically'.

[34] From October 1916 to February 1917, a spontaneous Serbian uprising broke out in the Bulgarian-occupied territories of southern and eastern Serbia, notably in the valley of the Južna Morava, on Mount Kapaonik and in Kosovo.

The scheme was identical to that previously pursued by the Serbian army,[36] which in August 1914 had attempted to conscript more than 60,000 people from Macedonia on the frontline defense of Serbia against the Austria-Hungarian attack.

By 3 March guerilla units made of local inhabitants had liberated Kuršumlija and Prokuplje as well as regions in the areas of Vlasotince and Sokobanja, coming 9 km southwest of Niš.

Austro-Hungarian, German and Bulgarian troops were brought from the Macedonian and Italian front,[40] while in the Mitrovica district, Albanian gendarmes were sent to track down rebel leaders.

[45] On 28 March Protogerov declared an amnesty, promising internment instead of execution; none of the prominent Serb guerrilla and military leaders surrendered and continued instead guerilla actions on the occupiers throughout the rest of the war.

Greek and British forces joined in, the Bulgarians, deprived of German and Austrian support, quickly found themselves in full flight, pursued by the Army of the Orient.

[11] The Serb army returned in 1918 to find a land devastated by war and exploitation; besides losing 210,000 men of its armed forces, Serbia suffered an additional 300,000 civilian casualties out of a 3.1  million population, material losses were incalculable.

[48] After the defeat of Bulgaria and the return of Macedonia, the Slav population of the area was declared Serbian and Bulgarian cultural, religious, and educational institutions were closed down.

[50] The reports of the commission in Eastern Macedonia summarised the violations of the Hague Conventions: the massacre of the civilian population, torture, rape, internment, punitive economic expropriation, requisitions, and various taxes, plunder, forced labor, destruction, arson, and other actions aimed at "destroying the Serbian presence in the newly occupied territories".