[1] Originally commissioned into the Intelligence Corps in 1963, he transferred to the Parachute Regiment in 1970, with which he served two of his three tours of duty in Northern Ireland.

On his second, he was a company commander in the aftermath of the Warrenpoint ambush (1979), when the IRA killed 18 soldiers with two roadside bombs, the British Army's heaviest single loss of life during the Troubles.

He returned to the Balkans with the ARRC during the Kosovo War, during which he famously refused to obey an order from American General Wesley Clark, his immediate superior in the NATO chain of command, to block the runways of Pristina Airport and isolate the Russian contingent that was positioned there.

The incident attracted controversy, particularly in the United States, and earned Jackson the nickname "Macho Jacko" in the British tabloid press.

Upon his return to the UK, Jackson was promoted to full general and appointed Commander-in-Chief, Land Command, the second-most senior position in the British Army.

After three years as Commander-in-Chief, Jackson was appointed Chief of the General Staff (CGS), the professional head of the British Army, in 2003.

[8] While at Sandhurst, he became increasingly interested in the Parachute Regiment, but eventually applied to, and was commissioned into, the Intelligence Corps as a second lieutenant at the age of 19.

[16][17] Jackson went on to serve in Northern Ireland as adjutant to 1st Battalion, The Parachute Regiment (1 PARA), and was present at the events of the Ballymurphy massacre, where 11 unarmed civilians were shot dead by British troops in August 1971[18] and at the events of Bloody Sunday, 30 January 1972, when 14 unarmed civilian civil rights protesters were shot dead by soldiers from 1 PARA in Derry.

[5] He was appointed Member of the Order of the British Empire (MBE) in the 1979 Queen's Birthday Honours[22] and was mentioned in despatches in 1981, in recognition of his service in Northern Ireland.

During his tenure at Camberley, he was seconded to a staff position at the Ministry of Defence in 1982 during the Falklands War, and thus missed the opportunity to serve in the conflict directly.

[5][28] He was persuaded to try again the next year and was promoted to brigadier on 31 December 1989,[29] after spending six months on a Service Fellowship writing a paper on the future of the Army and taking the Higher Command and Staff Course.

[12] Jackson retained command of the 3rd Division until July 1996 and went on to serve briefly in a staff post as the Army's Director General of Development and Doctrine.

[36] After he was appointed Commander of NATO's Allied Rapid Reaction Corps (ARRC), Jackson was promoted to acting lieutenant general in January 1997,[37] a rank he was granted substantively in April 1997.

He gained significant media attention in June 1999 after a confrontation with Clark in which he backed Captain James Blunt's refusal to block the runways of the Russian-occupied Pristina Airport and isolate the Russian troops there, thus preventing them from flying in reinforcements.

[39] The point became moot when the US government prevailed upon neighbouring countries, including Hungary and Romania, to prevent Russian use of their airspace to fly in reinforcements.

[3][43] Following the confrontation with Clark, Jackson went to the airport to meet Viktor Zavarzin, the Russian general leading the detachment, and established a working relationship with him.

He also handled requests from the civilian authorities for assistance with the foot-and-mouth disease crisis, floods and strikes by firefighters and fuel tanker drivers.

He managed to return to the UK the next day aboard a casualty evacuation aircraft and had overall responsibility for force generation for the British Army's contribution to the subsequent wars in Afghanistan and Iraq.

[5] Shortly after the invasion of Iraq, Jackson ordered an inquiry into the alleged abuse of Iraqi prisoners by British soldiers.

Several soldiers were eventually convicted in connection with the abuse, after which Jackson publicly apologised on behalf of the British Army and promised to appoint an officer to determine what lessons needed to be learnt.

[5][52] Jackson insisted that the change was necessary to give the Army greater flexibility and capability, but said he was "acutely aware that this will be sad and unwelcome news for at least some of the infantry".

[42] Jackson was dismissive of claims that the Army was under-equipped, recalling his conversation with a soldier: "There's a bit of a fuss going on about boots and bog rolls and whatnot.

[5] Known for speaking his mind,[1] Jackson attracted media attention towards the end of his tenure as CGS in 2006, when he criticised Norman Kember for his apparent lack of gratitude to the soldiers who freed him from Iraqi kidnappers.

[64] Following their amalgamation in the modernisation of the regimental structure, Jackson was appointed to the newly created position of Honorary Colonel, the Rifle Volunteers, in 1999.

[65] He was given the title of Aide de Camp General (ADC) to Queen Elizabeth II in 2001, succeeding Sir Rupert Smith.

Gary Sheffield, writing in The Independent, called the book "an engaging and honest account that would repay reading by all those who seek to understand the 21st-century British Army",[71] but Peter Beaumont, foreign affairs editor for The Observer, called it "disappointing" and commented that "in the end it is Jackson's opinions ... rather than any powerful new detail that emerges".

[5] He appeared on BBC Radio 4's series Great Lives, along with Major General Julian Thompson, RM, in 2008 and nominated Field Marshal Bill Slim.

[74] Jackson re-appeared in the headlines when he and other retired generals, including Major General Tim Cross, who was involved in the planning effort and later commanded all British troops in Iraq, criticised the American post-war planning for Iraq and attacked the statement by Donald Rumsfeld, US Secretary of Defense, at the time of the invasion, that the US does not "do nation-building", calling it "nonsensical" and "intellectually bankrupt".

[80][81] After the Saville Report published its findings in June 2010, Jackson gave an interview in which he joined the Prime Minister, David Cameron in offering a "fulsome apology" for the events.

He acknowledged that troops of the First Parachute Battalion, of which he was adjutant, had killed people "without justification", but went on to observe that "Northern Ireland is a very different place [in 2010], not least because of sacrifices made" by the soldiers who had served there, and asked that the report "be seen in this context".