Complex sentence: By nature a cautious general, Schwarzenberg was also jittery about his lengthening supply lines stretching back to the Rhine, which partly explains the Army of Bohemia's slow five mile per day advance.
Split into simpler sentences: By nature a cautious general, Schwarzenberg was jittery about his lengthening supply lines stretching back to the Rhine. This partly explains the Army of Bohemia's slow five mile per day advance.