Which prime minister extricated the British state from a futile, 30-year-long counter-insurgency war in northwestern Europe? And which prime minister then enmeshed the armed forces in a futile, decades-long counter-insurgency war in the Gulf?
The answer is Tony Blair.
Just as one set of British army fortifications is dismantled along the southern border of County Armagh, British army engineers dig into the Iraqi sand for another long war. Pointedly, the army's mothballed fleet of armoured Land Rovers, once ubiquitous in Northern Ireland, is on its way to southern Iraq.
The other parallels between "liberated Iraq" and Ireland are equally depressing; every day heralds a steady drumbeat of ambushes and minor skirmishes against the occupying British and American forces that is all too reminiscent of the Troubles. The battle for civilian hearts and minds is already largely lost in the Sunni and Shia communities. And spectacular assaults on soft targets such as the UN compound in Baghdad have hampered US efforts to win international support for its occupation.
The US war plan was predicated on the assumption that a liberated Iraqi could be swiftly pacified and power transferred to an interim, pro-American, Iraqi-led administration. Within months, most of the troops would be on their way home. But as the lessons of Ulster prove, under the assault of revolutionary violence all attempts to impose complex, artificial political structures are doomed to collapse.
Tony Blair's greatest achievement as Prime Minister has been his deft resolution of the perennial "Irish question". Now, his greatest failure may be a similarly endless occupation of Iraq. We have swapped Belfast for Basra. For all its warts and halting suspensions, the Good Friday Agreement marked the end of our Irish war. More so than any other British prime minister, living or dead, Blair grasped the central problem of the Troubles: that the power of small, impoverished armed groups using revolutionary violence was always greater than the powers of the state to resist them. For political reasons, the strategic power of violence in Northern Ireland was deliberately played down. But on the ground it was another story.
In daylight, the IRA was never a significant military threat to the British army, but the IRA's ability to keep blowing up Belfast's Opera House, plant car bombs near barracks and murder judges continually destabilised every British attempt to resurrect democratic politics. Normality was armed foot patrols, helicopter gunships along the border, hundreds of political/terrorist prisoners and the retreat of the state into IRA-mortar-proof bunkers.
Nor was the Provisional IRA the only actor on the Ulster stage. The loyalists were never more than simple murder gangs, but when they started machine-gunning Taigs (Catholics), the Provisionals felt compelled to respond with operations such as the disastrous 1993 Shankill bomb that prematurely detonated, killing nine civilians. The IRA plan had been for the bomb to kill the Ulster Defence Association leadership, which was meeting in a room upstairs. The IRA failed and, in revenge, the UDA went on the rampage - killing more Catholics.
The Troubles went on and on because the reverberating violence cut the feet from under every political representative. There was never a consensus, just a repetitious squabble for three decades over who was to blame for the latest killings.
The rules of engagement in a white island off the shores of Europe that enjoyed good media links precluded the British armed forces' usual brutal response, used in previous anti-colonial struggles. Military force had to be cloaked in civilian law, thus ruling out widespread assassination campaigns against IRA leaders or draconian mass screening operations against the nationalist community. Torturing suspects was illegal.
Wisely, Britain's political leadership sought to restrain the army for fear of widening the IRA's support base within the Irish island's borders. Everyone knew that shelling the Bogside would be a big mistake. But the failure to dominate territory allowed the IRA to swim like fish through the nationalist sea.
For 30 years, the IRA's ragtag volunteer army of never more than 600 outwitted and outbombed the 50,000-strong security forces. Twice the IRA came close to killing the entire British cabinet, while the three City of London bombs in the early 1990s seriously damaged the UK economy. The IRA could not win, but could not be defeated.
Comparisons with Iraq are dismaying. Ulster has a population of 1.5 million; Iraq 24 million, the majority of whom are hostile to the US and British invasion and occupation of their land.
Iraq's divisions - historic Sunni supremacy, secessionist Kurdish nationalism, Shia martyrology and the lure of a Bin Laden-inspired pan-Islamic jihad - create a more complex tapestry than the straightforward Protestant v Catholic hatreds that underpinned the Troubles.
Millions of Iraqi men have received rudimentary military training, and Iraq is awash with small arms and excess munitions from Saddam Hussein's demobilised forces. Guns and bombs, and the grievances to use them, are not hard to find. By contrast, the combined US-British occupation force numbers roughly 160,000 and is badly overstretched. But substantial increases in troop numbers, to the 400,000 level argued for by some US military chiefs, are politically unacceptable to the Bush administration and out of the question for the slimline British army.
Despite awesome intelligence capabilities, the US military has remained remarkably vague in public about the identity and political affiliations of the Iraqi resistance. Attacks are attributed to former Ba'athists or unspecified pro-Sunni elements of the old regime, or foreign "jihadists". Last month, the US closed the Syrian border to men of military age, to halt the inflow of potential fighters. But the sprawling number of those hostile to the US occupation is worrying. In Ireland, the British knew the names and postcodes of every IRA member - and still could not win.
Inevitably, the fate of Britain's armed forces in Iraq is bound up with the US military. As with the IRA in Ulster, each ambush against allied forces is militarily insignificant, and the drip-feed of casualties easily sustainable. But as the sounds of ambush grow louder by the month, the US military, even in relatively secure areas such as central Baghdad, is confined to its full-on offensive role. The Americans have largely abandoned the streets.
Unlike the British army in Ulster, US commanders feel under no compunction to restrain their troops' firepower. Western journalists have reported a stream of indefensible military search operations resulting in needless civilian casualties.
The response of the US military authorities to these mini-atrocities has been to suppress hostile media coverage, mirroring the British government's broadcasting ban in Ulster. The two major Arab satellite channels, al-Jazeera and al-Arabiya, have had their operations curtailed in Iraq. But in the era of modern communications, media restrictions are hard to enforce.
Using another standard guerrilla tactic, the resistance has started an assassination campaign against "collaborators", killing police chiefs and fatally wounding the US-appointed Iraqi Governing Council member Aqila al-Hashimi, one of only three women on the council, outside her home in Baghdad. The assassination of the Shia leader Ayatollah Baqr al-Hakim, which caused the deaths of 83 civilians outside the Imam Ali mosque in the holy city of Najaf, also appears to be designed deliberately to provoke internecine Sunni-Shia strife.
But the most significant act of insurgency was the August bombing of the UN headquarters, which killed 23, including the UN's chief representative, Sergio Vieira de Mello. That suicide attack, and the follow-up bombing of the Baghdad Hotel, in effect scuppered further international involvement in Iraq and isolated the occupation regime. If UN agencies return to Iraq, they will be able to do so only under the US military umbrella, in secure facilities, as another arm of occupation. And even the friendliest of pro-American allies is likely to baulk at sending troops in the face of such determined, potentially suicidal Iraqi resistance.
In classic counter-insurgency warfare terms, the critical moment has passed. The "Baghdad bounce", the post-liberation honeymoon period, has faded and the nascent US-sponsored Iraqi institutions have failed to gain legitimacy. In the coming months, the fractious coalition of Iraqi interests on the US- controlled governing council will unravel under the sustained pressure of resistance attacks and harsh US/UK counter-measures. The American house in Iraq, like that of the British in Ulster, is built on sand. And there will be British squaddies in Basra long after Tony Blair has fallen from power.
Kevin Toolis is the author of Rebel Hearts: journeys within the IRA's soul (Picador, £7.99). Kevintoolis@hotmail.com