Complex sentence: Following a brief battle, the disorganized Austrians broke and fled toward Weesen, but the collapse of the bridge over the "Maag" or "Weeser Linth" dropped much of their army into the river where they drowned.
Split into simpler sentences: Following a brief battle, the disorganized Austrians broke and fled toward Weesen. The collapse of the bridge over the "Maag" or "Weeser Linth" dropped much of the Austrian army into the river where they drowned.