According to journalist David McKittrick in his book Lost Lives, Hanna, at an early age became "obsessed with guns and military paraphernalia in general".

He would have been fast tracked on a refresher course to sharpen up his military skills, and would have been part of the UDR's front line of experienced soldiers when the regiment began duties in 1970.

[12] On 23 October of that same year, an armed UVF gang raided King's Park camp, a UDR/Territorial Army depot in Lurgan, and stole a large cache of sophisticated guns and ammunition.

A member of the UVF's Brigade Staff (Belfast leadership) on the Shankill Road, Hanna was described by journalist Joe Tiernan as having been a "brilliant strategist and an able leader".

[14] A Garda Síochána document dating from 1974 to 1975 revealed that the Republic's police knew Hanna was the Officer Commanding (OC) of the Mid-Ulster Brigade's Lurgan unit.

[2] Tiernan alleged that Hanna personally recruited and trained young men from the Lurgan and Portadown areas who were "prepared to defend Ulster at any cost".

[6] He then began carrying out bank and post office robberies, and intimidated local businessmen into paying protection money to the Mid-Ulster UVF.

[16] The name is derived from a farm in Glenanne, County Armagh (owned by James Mitchell, an RUC reservist),[17][18] which was used as a UVF arms dump and bomb-making site.

The Defence counsel described Hanna as a "former British Army soldier with a distinguished career in the Royal Ulster Rifles,[4] having served in the Korean War".

[21] RUC Special Patrol Group officer John Weir named Hanna, along with senior UVF member Robin Jackson and Davy Payne (UDA Belfast), as having led one of the two teams that bombed Dublin on 17 May 1974.

[27] It was stated in the Barron Report that former British soldier and psychological warfare operative Colin Wallace also suggested that Hanna had been the principal organiser of the Dublin car bombings.

In July 1993, a Garda detective received information from a reliable source that on 15 May 1974, a meeting had taken place inside the Portadown Golf Club in connection with the Ulster Workers' Council (UWC) strike; the same informer added that a separate meeting was held in the club which was attended by Hanna and Samuel Whitten, a suspect in the Monaghan bombing.

[31] The Monaghan bombing had been organised as a diversionary tactic to draw Gardaí away from the border, enabling the bombers to cross back into Northern Ireland undetected.

[25] According to submissions received by Mr. Justice Barron, the Monaghan bomb was assembled at the home of high-ranking UVF member Harris Boyle in Portadown.

Middle-ranking officers of the Intelligence Corps based at Army headquarters in Lisburn were frequent visitors to his Houston Park home in Lurgan's Mourneview estate.

These UVF men, from the Portadown and Lurgan areas as well as Belfast, had taken part in the Dublin and Monaghan attacks; they all confirmed that Hanna was the mastermind behind the bombings and that army officers were involved in the operation.

[37] Tiernan alleged that on the morning of 17 May 1974, Hanna and Jackson transported the bombs across the border into the Republic of Ireland in the latter's poultry lorry having retrieved them from James Mitchell's farm in Glenanne where they had been constructed and stored.

[25] The cars had been hijacked and stolen earlier that morning in Belfast by a local UVF gang known as "Freddie and the Dreamers"[39] which was allegedly led by William "Frenchie" Marchant.

[41][42] With the devices armed and each boot laden with its lethal cargo, Hanna then gave the final instructions to the drivers of the three car bombs and they set off on their mission towards Dublin's crowded city centre.

[43] Upon their return they went back to the soup kitchen they were running at a Mourneville bingo hall; the UWC strike was in its third day making it extremely difficult for people throughout Northern Ireland to obtain necessities such as food.

[45] Most of the dead were blasted beyond recognition; one girl who had been near the epicentre of the Talbot Street explosion was decapitated and only her platform boots provided a clue as to her sex.

[25] After the blasts the bombers fled from central Dublin in the scout cars and headed back north using the "smuggler's route" of minor and back roads, crossing the Northern Ireland border near Hackballs Cross, County Louth at about 7.30 p.m.[25] Thirty minutes earlier, a fourth car bomb, delivered by a team from the Mid-Ulster UVF's Portadown unit, had exploded in Monaghan, killing an additional seven people.

[53] Mr Justice Henry Barron's opening statement to Oireachtas Joint Committee on 10 December 2003, described the Dublin and Monaghan bombings as the "most devastating attack on the civilian population of this State to have taken place since the 'Troubles' began".

According to a senior UVF figure in Armagh, who had not been involved in the bombings but who had played a leading role in a number of other operations by the Mid-Ulster Brigade, Hanna would frequently visit his house in the aftermath of the attacks and would cry about "all those children killed in Dublin".

[56] Anne Cadwallader in her book Lethal Allies British Collusion in Ireland states that the pistol used was a Webley which was recovered in a hedge outside Portadown on 11 November 1976.

[59] Hanna was allegedly shot after he had refused to participate in the UVF's planned Miami Showband attack, which Jackson had personally organised and would help to carry out on 31 July.

[60] Dillon opined that Jackson's accomplice in the shooting was UVF Major Harris Boyle, who would be blown up in the Miami Showband attack four days later.

Investigative journalist Paul Larkin in his book A Very British Jihad: collusion, conspiracy, and cover-up in Northern Ireland also said this, adding that Jackson shot Hanna after learning that he had passed on information regarding the Dublin and Monaghan bombings.

[61] Dillon suggested that because a number of UDR/UVF members were to be used for the Miami Showband ambush, Hanna was considered to have been a "security risk", and therefore had to be eliminated before he could alert the authorities.

"[63] Jackson attended Hanna's funeral on 29 July where he was photographed standing beside Wesley Somerville, the second bomber who would be killed in the Miami Showband attack.