The Arms Crisis was the most direct threat to democracy in this State during the past 50 years and arguably the most serious political conflict since the Civil War.
But, while the continuing release of State papers in Dublin, Belfast and London adds to our knowledge of the detail, there's a danger we may forget where the threat began and how it grew.
The immediate threat in late 1969 and early 1970 lay in the existence of a government-within-a-government, with competing claims to the leadership of the Fianna Fail party and what is sometimes called the nationalist family.
The government-within-a-government, itself a coalition of sorts, was formed, as we now know, by Neil Blaney and Charles Haughey following attacks on Catholic areas in Belfast in August 1969.
Reports of disagreement in the cabinet had appeared from time to time before the attacks began and were to appear more often afterwards. Taoiseach Jack Lynch's most vociferous critics, according to these accounts, were Blaney and Kevin Boland; Haughey was never mentioned.
This was hardly surprising. The most obvious issue dividing the factions was "the North". And Blaney, whose militant views were well rehearsed, was widely known to have Boland's support. Even erstwhile cabinet colleagues were to comment on Haughey's silence.
But neither Blaney nor Haughey had lost any of their ambition since the 1966 leadership contest and, like Boland, fiercely resented the party's choice of Lynch, whom they saw as an outsider.
Lynch had accepted - and had largely followed - the advice that T.K. Whitaker had offered on North-South policy in 1968: there was no valid alternative to the policy of seeking "agreement in Ireland and between Irishmen".
It was a long-term policy, as Whitaker acknowledged, requiring "patience, understanding and forbearance". And it called for resolute resistance to "emotionalism and opportunism", the traps into which nationalist Ireland was about to march.
In the high excitement of August 1969 it was understandably difficult for patience and forbearance to succeed. But an opportunity was handed to those who held Lynch's leadership in contempt and rejected Whitaker's advice.
A cabinet committee was formed to handle Northern affairs. Haughey and Blaney were soon in control of it. A fund of £100,000 was set up to relieve distress in Northern Ireland. Haughey was to administer it. Haughey and the minister for defence, Jim Gibbons, were to ensure the Army had the equipment and resources it needed. It was on Blaney's advice that Gibbons ordered the movement of arms to Dundalk in 1970.
It was to Blaney and Haughey that Capt James Kelly of Military Intelligence reported at key points in the events which led eventually to two trials on charges of conspiracy to import arms. Haughey, James Kelly and their fellow defendants - Belgian businessman Albert Luykx and Belfast man John Kelly - were acquitted by jury in the High Court. A lower court had decided Blaney had no case to answer.
But the most significant action of the government-within-a-government was Haughey's meeting with the British ambassador, Sir Andrew Gilchrist, at Kinsealy in the first week of October 1969.
It was the subject of a report to the Foreign Office on November 10th, 1969, quoted in The Irish Times in January 2000 and summed up by Justin O'Brien in The Arms Trial (Gill and Macmillan) just published: "Haughey had a proposal he wished London to consider. In return for British support for a united Ireland, he offered British access to the old treaty ports, or, alternatively, NATO access to them.
"According to Gilchrist, Haughey wanted a secret commitment that the Border would be the subject of an inter-governmental review. Gilchrist told his superior that Haughey - whom he described as able, shrewd and ruthless - was insistent there was `nothing he would not sacrifice, including the position of the Catholic Church, to achieve a united Ireland' ".
Here was the leader of the government-within-a-government acting as if he were Taoiseach, making an offer for which he would certainly have castigated his opponents. O'Brien notes the irony that it was made in the same week as the meeting at Bailieborough which has been described as the genesis of the plot to import arms.
Lynch may properly be criticised for the roles allocated to Blaney and Haughey. Gibbons's decisions are being questioned once more in the light of military intelligence files released this week.
Little has been disclosed about the extraordinary failure of the minister for justice, Micheal O Morain, to inform Lynch of the activities of his colleagues, of which he was almost certainly aware. O Morain's resignation started the week in which Haughey and Blaney were sacked and Boland resigned.
The reason given for O Morain's departure was ill health. It was not the whole truth: he had been under heavy personal and political pressure for several months and, as Lynch disclosed later, would have been dismissed had he not resigned.
It is now clear politicians and police had their sights on the wrong targets in the late 1960s. They saw the decision of some republican leaders to concentrate on housing and resources as an ominous threat from the left, not as a move away from militarism. And O Morain failed to identify the threat that existed closer to home.