Although he follows no rules, we know Satan attacks on three fronts: through the flesh, through the world, and by direct assault. The Flesh:
In the 1936 Spanish civil war, Franco’s Loyalist Army defeated the Republican Army in Madrid. It was the key battle of the war and led to the establishment of Franco’s gov’t in Spain.
When asked what the key to victory was, he replied, "The fifth column." He had 4 columns of troops engaged openly and a fifth column of loyalists inside who, through sabotage, seriously weakened the Republican Army.
Satan has a fifth column - the sinful passions that reside within us.
From Gregory McDonald Sr. ’s Sermon “Power Encounterâ€