Complex sentence: When they attempt to take the town of Olomouc they were beaten by the Czech royal army in a battle of Olomouc, and Baidar were killed by King Václav, then rest continued via Brno, to join Batu's main army in Hungary.
Split into simpler sentences: When they attempt to take the town of Olomouc they were beaten by the Czech royal army in the Battle of Olomouc, and Baidar was killed by King Václav. The rest continued via Brno, to join Batu Khan's main army in Hungary.