The use of aircraft in the close air support of ground forces dates back to the First World War, the first conflict to make significant military use of aerial forces. Air warfare, and indeed aviation itself, was still in its infancy—and the direct effect of rifle caliber machine guns and light bombs of the First World War aircraft was very limited compared with the power of (for instance) an average fighter bomber of the Second World War, but CAS aircraft were still able to achieve a powerful psychological impact. The aircraft was a visible and personal enemy—unlike artillery—presenting a personal threat to enemy troops, while providing friendly forces assurance that their superiors were concerned about their situation.