The Irish Volunteers in County Clare had been active since 1917. By late 1920, after months of attacks on isolated Royal Irish Constabulary barracks, the RIC had abandoned most of its small rural posts in the county. The British government's answer was to flood Clare with Black and Tans - hastily recruited British ex-soldiers in dyed uniforms - and the more elite Auxiliaries. By the time of the ambush, five RIC men, eleven IRA volunteers, and four civilians had been killed in the county over the previous two years.

The IRA's Mid Clare Brigade had noticed a pattern: a single RIC lorry travelled the road between Ennistymon and Milltown Malbay once a week. John Joe Neylon, the local battalion leader, was put in charge of the ambush. The actual attack was led by Ignatius O'Neill, the brigade's Officer Commanding - a veteran of the Irish Guards in the First World War. The party had nine rifles, some grenades, and shotguns and handguns for everyone else. They took position on a boreen above the road at Rineen and waited.

While the Mid Clare Brigade lay in wait, something happened twenty miles away that would shape what followed. Alan Lendrum, the local resident magistrate, was driving toward Doonbeg when he came to a railway crossing at Caherfeenick. The West Clare Brigade - a separate IRA unit - had set up an unrelated roadblock. They demanded Lendrum surrender his car. He drew an automatic pistol. They shot him twice in the head.

He was a man with a job and a name and probably people who loved him. The IRA weighted his body with stones and dumped it in a nearby lake. A British military inquest later established the cause of death as gunshot. RIC officers in Clare nevertheless spread a story that Lendrum had drowned. The killing was not part of the Rineen ambush plan and the two battalions had not coordinated. But Lendrum's disappearance was noticed quickly, and the British military in Ennistymon dispatched ten lorries of soldiers to find him - lorries that would arrive at Rineen just after the ambush ended.

The single RIC lorry passed safely through the ambush position on its way from Ennistymon to Milltown Malbay - confusion in the IRA party about whether more vehicles were behind. When they understood it was only the one, they prepared for its return. The lorry was hit by a grenade and then by close-range rifle and shotgun fire. Five RIC men were killed outright. The sixth got out and ran. He was shot down 300 yards on. Five were Irish RIC officers. One was an English Black and Tan. The IRA took their weapons, set fire to the lorry, and prepared to leave.

Then the ten British Army lorries arrived, expecting to be searching for Lendrum. A running fight broke out. Four IRA riflemen kept the soldiers at bay while the rest of the party withdrew in an orderly retreat. Two IRA volunteers were wounded. Several British soldiers were also wounded. The ambush had lasted about twenty seconds. The fighting that followed lasted long enough for the IRA to disappear into the County Clare hills. The Mid Clare Brigade had executed a textbook engagement against a vastly larger force. What came next was not a battle.

Within hours, British forces went looking for revenge. They burned the O'Gorman family's house and farm. They shot a local farmer, Sean Keane, who died of his wounds. That same night, a mixed force of police and soldiers raided the home of Dan Lehane in Lahinch - his two sons had been in the ambush party. They shot Dan dead and set fire to his house. His son Patrick Lehane, who was inside, burned to death in the attic. Several other houses in Lahinch were burned. Eight more were razed in Milltown Malbay.

Another raid hit Ennistymon. Tom Connole, secretary of the local Irish Transport and General Workers' Union branch, was killed and his home burned. PJ Linnane, a fifteen-year-old boy, was shot dead by the police. The Labour Party in the House of Commons tabled a resolution condemning the reprisals and calling for an investigation. The resolution was defeated, 346 votes to 79. The Chief Secretary for Ireland, Hamar Greenwood, told the House the burned houses had belonged to "notorious Sinn Feiners" and that the people of those villages had known of the ambush in advance. He was lying about the burned houses. He may or may not have been right about advance knowledge.

On 22 September 1957, thirty-seven years to the day after the ambush, a cut-stone monument depicting an IRA soldier was unveiled at Drummin Hill by the Bishop of Killaloe. The cost - just over 1,200 pounds - was raised by veterans, public subscription, and Irish-Americans in the United States. Ignatius O'Neill, then in his sixties, gave a short address. Dr Patrick Hillery, then a young politician who would later be President of Ireland, was in the crowd.

The centenary in 2020 was muted by COVID restrictions. A deferred 100th-anniversary commemoration on 22 September 2023 was addressed by Micheal Martin, then Tanaiste, and a plaque to Commandant Ignatius O'Neill was unveiled on Milltown Malbay's main street. At the ninetieth anniversary, the Minister of Defence Tony Killeen had welcomed descendants of the six RIC officers killed in the ambush, naming the dead on both sides. The Catholic priest Sean Gaynor, looking back on the whole episode, said of Alan Lendrum's death in particular that it "was not to our credit." After his body was recovered from the lake, the local IRA placed it in a roughly made coffin and left it on the tracks at Craggaknock railway station for British forces to find.