Before they even get fully into formation, Roland's cannons already start bombarding them.
They charge, but the cannon group just switch to grape shot shell and basically beehive'd the groups that got closer.
On their retreat, Roland's army constant kept a certain pace away, to ambush them when the coalition force try to rest (Lightning is in charge of recon so she can ensure Roland's forces are always just outside of the scout's range)
The coup de grace came with Roland using his concrete boat to set up ambush position ahead, on their way to Longsong.
Most people who fight back get shot, the rest get captured.
Petrov's father and the knight here survived btw