Blitzkrieg (German, "lightning war" listen) is an anglicised word describing all-motorised force concentration of tanks, infantry, artillery, combat engineers and air power, concentrating overwhelming force at high speed to break through enemy lines, and, once the lines are broken, proceeding without regard to its flank. Through constant motion, the blitzkrieg attempts to keep its enemy off-balance, making it difficult to respond effectively at any given point before the front has already moved on.
During the interwar period, aircraft and tank technologies matured and were combined with systematic application of the German tactics of infiltration and bypassing of enemy strong points. When Germany invaded Poland in 1939, Western journalists adopted the term blitzkrieg to describe this form of armoured warfare. Blitzkrieg operations were very effective during the campaigns of 1939–1941. These operations were dependent on surprise penetrations (e.g. the penetration of the Ardennes forest region), general enemy unpreparedness and an inability to react swiftly enough to the attacker's offensive operations. During the Battle of France, the French, who made attempts to re-form defensive lines along rivers, were constantly frustrated when German forces arrived there first and pressed on.
Academics since the 1970s have questioned the existence of blitzkrieg as a coherent military doctrine or strategy. Many academic historians hold the idea that the German armed forces adopted "blitzkrieg" as an offensive doctrine to be a myth. Others continue to use the word to describe the style of breakthrough warfare practised by the Axis powers of this period, even if it were not a formal doctrine. The concepts of Blitzkrieg form the basis of present-day armoured warfare.