This chapter investigates the intelligence war’s effectiveness against each regional IRA group between July 1972 and December 1975. Whilst the Belfast IRA suffered some operational difficulties because of British intelligence efforts, the Derry City IRA, rural republican units in Fermanagh, Tyrone and south Armagh, and the cells operating in England had not been damaged to any considerable extent by 1975. It is true that the number of deaths caused by the IRA had declined since 1972. But the republican movement had spread further across Northern Ireland and the borderlands of the Irish Republic. The IRA maintained a persistent campaign for reasons explored in this chapter. Northern Ireland remained politically unstable in 1975, and when the IRA called a prolonged ceasefire, this was not out of desperation. This chapter discusses important events in the intelligence conflict between 1972 and 1975, included the discovery by the IRA of the Four Square Laundry intelligence operation in Belfast in 1972.