Complex sentence: The tradition goes that at the first celebration hereof, they were suddenly invaded by the enemy, and obliged to take to their arms; upon which occasion a cloud of darts and arrows falling upon their enemies, the Romans soon returned victors to their sports.
Split into simpler sentences: The tradition goes that at the first celebration hereof, they were suddenly invaded by the enemy, and obliged to take to their arms. A cloud of darts and arrows fell upon their enemies, and the Romans soon returned victorious to their sports.