Lieutenant General Sean McCann made the recognition in a letter to a retired soldier, Michael Walker, who two years ago was told to stop writing to the Defence Forces with demands for a fresh inquiry into the tragedy.
The Chief of Staff said those who served alongside Corporal Fintan Heneghan, Private Tomás Walsh and Private Mannix Armstrong suffered when the three peacekeepers were killed in a landmine attack in the Lebanon on Mar 21, 1989.
But, in his recent letter, Lt Gen McCann accepted this had been compounded by the Defence Forces’ refusal to properly investigate what happened.
“I acknowledge the distress the incident itself caused but also the stress associated with the efforts to have a more comprehensive inquiry.
“The Defence Forces greatly regrets it has taken so long to finally bring these tragic events to a close for all concerned,” he said.
In Sept 2011 the independent ministerial inquiry of Frank Callanan found, despite the army’s position for 21 years, there had been a failure to properly assess the landmine risk.
Papers at the UN archives in New York also contradicted the army’s previous stance that there had been a limited threat of direct attacks on Irish soldiers by anti-Israeli fighters.
Families of the dead soldiers always maintained there had been a cover-up.
The inquiry was triggered in Apr 2011 when fresh evidence was uncovered just as the State was preparing to defend a damages case taken by Pte Armstrong’s widow.
The inquiry report supported many of the discrepancies uncovered by Mr Walker, who was part of the mine sweeping team in Lebanon in Mar 1989.
Lt Gen McCann said the three murdered soldiers were deployed in an unnecessarily high-risk scenario.
Mr Walker began working to uncover the truth about what happened in Braashit on Mar 21, 1989, after the army released an incorrect version of events to an RTÉ documentary in 2001.
Mr Walker said when he received the letter of Nov 22 he felt a sense of closure and would write to Lt Gen McCann to thank him for recognising the suffering of the soldiers of the 64th Battalion’s C Company.
“In some ways it’s better than the Callanan report because it acknowledged the distress of the families and the fellas who worked to get the truth out,” he said.