The attack on the night of 14/15 October 1944 by No. 5 Group Royal Air Force (RAF) marked the high point of the destruction of Henry the Lion's city in the Second World War. The air raid, part of Operation Hurricane, caused a large fire or conflagration, that may have developed into a firestorm,[citation needed] which resulted in Braunschweig burning continuously for two and a half days. Moreover, the attack destroyed Braunschweig's mediaeval city centre (more than 90% of it) thereby changing the city's appearance right down to the present day.