What does ambassador muccio mean by “all out offensive”?

John Muccio was the US Ambassador to Republic of  Korea when the Korean War between communist North Korea and Pro-west Republic of Korea broke out. On 25th June 1950 North Korea attacked ROK . Muccio termed the attack as all-out offensive owning to nature of attack and manner in which it was launched.  The North Korea attacked upon Rok heavily by using tanks and attacking on various fronts.

C, just took the test.