Complex sentence: Both men possessed the much coveted "coup d'œil militaire", the ability to see at a glance what must be done to tactical advantage, which allowed them to utilize the artillery and cavalry to full potential.
Split into simpler sentences: Both men possessed the much coveted "coup d'œil militaire", the ability to see at a glance what must be done to tactical advantage. This attribute allowed them to utilize the artillery and cavalry to full potential.