Leonidas Papapavlou was born in Siatista in 1866. His father was a priest and Byzantine Psalmist. Leonidas Papapavlou was taught to love God, Greece and consider the liberation of Macedonia his duty. When his father died and he had to support his family. He remained in the Monastery to help his family financially. Even Papapavlou offered to the Greek Consulate of the Monastery. The Turkish and Bulgarian authorities were informed of his action and ordered his arrest and his exile. The Turkish Police tried to arrest him, he left in Athens and enrolled in the philosophy faculty of the University of Athens. He was appointed Professor in Cyprus, his reputation as a scientist and educator spread and shortly afterwards Papapavlou came to the city of Serres, where he took over the management of the 1st Boys’ Gymnasium of Serres. Parallel to his educational activity, Papapavlou also developed a national, especially during his time Bulgarian occupation. In 1912, the Bulgarian troops occupied Eastern Macedonia and committed serious crimes. In Serres, the military director of the Bulgarians ordered Leonidas Papapavlou to take down the Greek sign from the Serres High School and replace it with a Bulgarian one. But he refused and did not give in. A committee was set up in Serres which tried to prevent the city of Serres from remaining under Bulgarian occupation, consisting of Leonidas Papapavlou as the President. In the meantime, the Bulgarians began to arrest and imprison various residents of Serres. They arrested the Metropolitan of Serres, Leonidas Papapavlou and other Serres. The arrested were subjected to horrible torture. Leonidas Papapavlou was martyred at the age of 47 on June 29, 1913. He was an example of heroism, self-sacrifice and devotion to duty.