Complex sentence: In three weeks of fierce battles, 8,000 Spanish troops were killed, and by July, the Spanish army of 13,000 was forced to flee to the coast, and into Melilla, defeated by an army of 3,000 Rifian fighters.
Split into simpler sentences: In three weeks of fierce battles, 8,000 Spanish troops were killed. By July, the Spanish army of 13,000 had fled to the coast, and into Melilla, defeated by an army of 3,000 Rifian fighters.