In 1395 the Ottomans attacked Wallachia to punish its ruler, Mircea I, for his incursions into their territory. Three Serbian vassals fought on the Ottoman side: King Marko, Lord Konstantin Dragaš, and Despot Stefan Lazarević (son and heir of Prince Lazar). The Battle of Rovine, on 17 May 1395, was won by the Wallachians; Marko and Dragaš were killed. After their deaths the Ottomans annexed their lands, combining them into an Ottoman province centred in Kyustendil. Thirty-six years after the Battle of Rovine, Konstantin the Philosopher wrote the "Biography of Despot Stefan Lazarević" and recorded what Marko said to Dragaš on the eve of the battle: "I say and pray to the lord to help the Christians and for me to be among the first to die in this war." The chronicle goes on to state that Marko and Dragaš were killed in the battle. Another medieval source that mentions Marko's death at the Battle of Rovine is the Dečani Chronicle.