Complex sentence: Saladin intended a stealthy surprise attack at dawn, but his forces were discovered; he still attacked, but his men were lightly armored and suffered heavy casualties due to Crusader crossbowmen.
Split into simpler sentences: Saladin intended a stealth and surprise attack at dawn, but his forces were discovered. Saladin still attacked though, but his men were lightly armored and suffered very heavy casualties due to the Crusader crossbowmen.