For a long time，people feel puzzled on Egyptian actions before the third Middle East war and their poor performance in the war. Most of the existing explanations hold the military regime of Nasser as an internal unity，they play down the differences between the military and government in Egypt，and ignore a power struggle between President Nasser and Commander in Chief Amin. Since 1961，there has been deep dissatisfaction between Nasser and Amin，those tensions and disagreements manifested in three areas：military regime，corporate issues and security strategy. In order to strengthen the control on the army and personal power，Amin selectively delivers information to Nasser，deliberately ignores strategic coordination with the government，refuses to implement certain decisions made by Nasser，these provokes Israel to launch a war. Civil-military division caused some army officers with low competitiveness，ill-prepareness for war，and poor performance in the war，reducing the military effectiveness and leading to the catastrophic defeat.