Pilots soon learned to achieve a firing position (while avoiding the threat of enemy guns) by manoeuvring themselves behind an enemy aircraft; this is known as getting onto an aircraft's "six o'clock" or onto their "tail", plus a wide variety of other terms, usually coined by air crew. This type of combat became known as dogfighting. Oswald Boelcke, a German fighter ace during World War I, was the first to publish the basic rules for aerial combat manoeuvring in 1916, known as the "Dicta Boelcke". He advised pilots to attack from the direction of the sun (toward which the defending pilot could not see), or to fly at a higher altitude than the opponent. Most of these rules are still as valuable today as they were a century ago.