Complex sentence: The commander of JNA forces in the first phase of the battle, Gen. Aleksandar Spirkovski, was a Macedonian; his ethnicity was probably a significant factor in the decision to replace him with Života Panić, a Serb.
Split into simpler sentences: The commander of JNA forces in the first phase of the battle, Gen. Aleksandar Spirkovski, was a Macedonian. His ethnicity was probably a significant factor in the decision to replace him with Života Panić, a Serb.