The Iran-Iraq War was one of the bloodiest conflicts of the 20th Century and accidentally created the current nightmare of Islamic fundamentalist terrorism. There have been many books on the conflict but this is the first detailed military history using materials from both sides, as well as materials obtained from US Intelligence circles and British Governmental archives. It provides a unique insight into a war which began through miscalculation and rapidly escalated into the longest conventional conflict in the post-Second World War era. Part 4 in this mini-series covers the warfare between Iran and Iraq on the Central and Northern Fronts. Difficult terrain made it problematic for either side to assemble overwhelming superiority. Following initial Iraqi attacks that seized some territory, the Iranians began gradually nibbling back until achieving some success in the centre, in 1982. Subsequently, the Central Front saw only minor conventional battles until Iraq launched several major blows in 1988. In the north, fighting primarily revolved around several Kurdish insurgencies in northern Iraq, and culminated in the horror of the Halabcheh gas attack. The final campaign of the war saw Iraq-supported Iranian émigrés launching a spectacular, but also a swiftly-crushed, invasion of their homeland.