Its founder, Charlie Sargent, was suspected by his followers of being an MI5 informant, leading to a split(some think the whole organization began as an MI5 operation meant to discredit the BNP, and to attract the UK's more violent Neo-Nazis). The new leader, Wilf "The Beast" Browning wanted to reconcile with him, but this attempt led to Browning being murdered by Sargent and Martin Cross, former Skrewdriver guitarist. Since then, the group has further splintered into the White Wolves and Racial Volunteer Force.
In 1999 a White Wolf, David Copeland, committed a series of three bombing attacks in London which targeted blacks, Bangladeshis and gays respectively.
Combat 18 is now largely a label used by semi-independent local chapters in various white-majority countries; however these usually serve more or less the same purpose as the original, that is, protecting Blood and Honour events.
In 2019 it was added to Canada's list of designated terrorist organizations. Because of its relative inactivity by this point, many suspect this was in reaction to the mosque shootings in Christchurch, and to send a message to other white identity extremists in Canada that they could possibly be designated terrorists.
The name originates from the initials for Adolf Hitler, A and H being the first and eighth letters of the alphabet respectively.