What is being described?

This is an extract from an article published in TIME magazine, in the issue dated September 25^th, 1939: “The battlefront disappeared, and with it the illusion that there had ever been a battlefront. For this was no war of occupation, but a war of quick penetration and obliteration - ________. Swift columns of tanks and armored trucks had plunged through while bombs raining from the sky heralded their coming. They had sawed off communications, destroyed stores, scattered civilians, spread terror. Working sometimes 30 miles (50 km) ahead of infantry and artillery, they had broken down the defenses before they had time to organize. Then, while the infantry mopped up, they had moved on, to strike again far behind what had been called the front.” What is being described and what term was coined in this article? –

GERMAN INVASION OF POLAND, BLITZKRIEG