Complex sentence: The operation was soon called off and the French forces withdraw to the lowlands, it was a tactical success, inflicting severe casualties on the Viet Minh, but strategically indecisive, because it failed to capture the Viet Minh leadership or seriously cripple its military forces.
Split into simpler sentences: The operation was soon called off and the French forces withdraw to the lowlands, it was a tactical success, inflicting severe casualties on the Viet Minh, but strategically indecisive. Because it failed to capture the Viet Minh leadership or seriously cripple its military forces.