The introduction of machine guns and artillery in the early 20th century led to trench warfare and the development by the British of primitive tanks, slow moving armored tractors bristling with machine guns or light cannon. While in individual battles the tank succeeded, lack of speed, logistics, and numbers prevented the British from exploiting their successes. After WWI, the German army took their enemy's work, altering and refining it. Germans aimed for fast, offensives vehicles designed to bypass enemy strong points and strike directly at their communication and supply system. The power of the Blitzkrieg, lightning war, had arrived.