Task: Question Generation
Input (English): Passage: The Serbian army emerged victorious, although details of the actual battle are vague. Şahin Bey entered Serbia with 20.000 akinjis at that time he learned that Serbian lords had prepared an army to attack his troops. He advanced to Pločnik near Prokuplje but could not detect the position of that army, and believed that there was none. At that time, many akinjis  lost their temper and began looting civilian properties in the surrounding villages by disobeying orders. Şahin Bey stayed alone with 2,000 soldiers. On the other hand, the battlefield was observed by Serbian expeditionary forces. Suddenly an allied army with 30,000 soldiers appeared, many of whom were cavalry. The Serbian army used heavy knight cavalry charge with horse archers on the flanks. The Serbs first attacked the Ottoman center , although they were unprepared and tasted nasty shock to heavy Serbian knights, the outnumbered Ottoman center resisted for some time but later began to withdraw with Şahin Bey who barely escaped with his life. Then the Serbian army turned to the other 18,000 akinjis that were busy plundering; unprepared, ill-disciplined, surprised akinjis couldn't do anything without their general. Only 5,000 of them returned home alive. More than 60% of the Ottoman army was destroyed. According to tradition Serbian knight and folk hero Miloš Obilić participated in this battle and distinguished himself, and was wounded by an Ottoman arrow. According to some, such as Croatian historian Vjekoslav Klaić, Lazar's army was aided by Bosnian troops. One version of the battle has it that the battle was won thanks to the Bosnian troops and the trickery of a Kastrioti.
Output (English): Which happened first, Sahin Bey entering Serbia or his advancement to?