The Valandovo affair was one of the largest crackdowns faced by the Internal Macedonian Revolutionary Organization (IMRO) in the late 19th century. It began on December 7, 1899, when Ivan Karasulijata and his IMRO unit entered Valandovo intending to rob a wealthy Greek individual. However, they were discovered, leading to a gunfight with Ottoman gendarmes, in which two officers were killed. The IMRO unit escaped without losses, but the incident triggered a massive Ottoman investigation.

The crackdown spread across Gevegelija, Tikvesh, Dojran, and Enidzhe-Vardar, resulting in the torture and arrests of around 100 people. The Ottoman authorities suspected a larger conspiracy, leading to widespread raids and brutal interrogations. Villages like Balinci, Gjavato, and Bogdanci suffered severe repression, with many locals beaten, arrested, or forced to flee. The affair crippled IMRO’s organizational network in the region, marking a major setback for the revolutionary movement.