Complex sentence: He sent Gustav Horn and a detachment of reiters to cross further to the West of the river to cover the flank, and attacked with his own force across the bridgehead and managed to rout the Poles positioned there.
Split into simpler sentences: He sent Gustav Horn and a detachment of reiters to cross further to the West of the river to cover his flank. With his own force he attacked across the bridgehead and managed to rout the Polish troops positioned there.