When it was originally published in 1984, Militant was widely acclaimed as a masterly work of investigative journalism. Although the rise of Jeremy Corbyn is to be attributed to more than hard-left entrism, to some within the party, Crick's book must seem like a lesson from history.Militant was a secret Trotskyite organisation that consistently denied being a party, though at its peak in the mid-1980s it could boast around 8,000 members, all of whom also belonged to the Labour Party. Militant operated clandestinely inside the Labour Party, edging out moderates at grass-roots level and recruiting people to its own ranks. Whilst eventually most of its leaders were expelled, it caused damaging rifts within Labour. Crick's book explores the origins, organisation and aims of Militant. It also explores the famous boss politics of Derek Hatton and Militant in Liverpool, and the party hierarchy's determined and ultimately successful attempts to squash the tendency.An important historical document, it is today seen as a field guide to how hard-left factions can infiltrate the Labour party, with some in the centre of the party allegedly urging its supporters to treat the long unavailable book as a 'war manual'.