Complex sentence: The Russian commander Lieutenant-General Nikolay Mikhailovich Kamensky was marching south when he learnt about the Swedish task force; he quickly wheeled around and marched north in order to face Wachtmeister's army before Wrede's arrived.
Split into simpler sentences: The Russian commander, Lieutenant-General Nikolay Mikhailovich Kamensky, was marching south when he learned of the Swedish task force. He quickly wheeled around and marched north to face Wachtmeister's army before Wrede's arrived.