Guernica's 6,000-strong population was swollen to some 10,000 on 26 April 1937, not just with villagers coming to market but with Basque troops and refugees retreating from Franco's approaching nationalist forces. There was uncertainty and fear in the air.
"Our teacher sent us home from school at midday, because he was worried something might happen," Inaki continues.
"Then as we were having lunch, at about 2pm, the church bells started to ring, which was how we sounded the alarm. I ran into the hills with some friends and about an hour later saw the first planes arrive, circling a few times and dropping their bombs."
Heinkels and Junkers of Hitler's Condor legion flew up the valley for more than three hours that afternoon, dropping bombs on Guernica's crowded market square and machine gunning its terrified citizens from the air.
The destruction prompted Picasso to produce his masterwork Guernica, which many consider this century's finest painting.
"The pilots came in so low that I saw their faces, their goggles, everything. They opened fire and there was no answering fire; we had no anti-air defence. I heard explosions, saw balloons of smoke. I was scared stiff," Inaki says.
It was Europe's first aerial bombardment of civilians, and a trial run for the subsequent destruction of Coventry, London, Warsaw and Dresden.
The targets were not strategic: Guernica's arms factories were spared and they still stand beside the railway line.
Pablo Izaquirre, who was then a 10-year-old altar boy on bell-ringing duty, hid in the spiral staircase of the church spire.
"I later spent 50 years of my life working in those factories, making pistols - Condor pistols they were called." He smiles at this irony of fate, although any rancour has softened with the years.
Between 500 and 1,000 people died that afternoon; no one knows the exact number.
"My sister was a nurse at the military hospital and said they couldn't tell how many died," Pablo said. "They loaded the bodies into carts and dumped them in the cemetery. Many remained beneath the ruins."
Inaki's eyes fill at the memory of what he saw when he scrambled down from the hills. "It was just rubble," he said. "Houses were burned by incendiary bombs and flames leapt from house to house. We were left in the street with nothing but the earth beneath us and the sky above our heads. Three days later, Franco's troops came in."
Eduardo Vallejo, Mayor of Guernica, is convinced that his city was blitzed because of its importance to the Basques: "Guernica is almost sacred for us, the cradle of our ancient rights and liberties. We have held democratic assemblies beneath our oak tree for hundreds of years."
He says Franco wanted to punish the Basques for not supporting his revolt against the republic the previous July: "But he was ashamed of what he had done," he said, "and accused the retreating Basques of torching their own city. He died without ever admitting the truth."
Inaki adds a postscript. "One day in September 1937, I was playing in the rubble and a couple of buses came up carrying smart men in uniform - Germans. They were Condor pilots. They asked us what we had seen that day and what had been where, and through an interpreter we told them. They seemed proud of their work. And I had to swallow this for 40 years for fear of imprisonment."
In recent years, local historians have tried to reconstruct events, assembling survivors' memories and scant documentary evidence. "We were concerned that our children were being taught about the mountains of Australia and the rivers of England but nothing about our own history," says Alberto Iturriarte, a teacher at Guernica's primary school.
"There were no books about Guernica, and the bombardment destroyed the town hall's local archives. We found a lot of material in Madrid in Franco's files on 'Destroyed Regions'. But we still don't know whose idea the bombardment was - the Nazis' or Franco's. Towards the end of Franco's dictatorship [in 1975], some Francoists said the act was imposed upon him by the Nazis. But there is no documentary evidence either way."
Guernica's ancient oak was spared, a gnarled stump protected in a little stone temple on a grassy knoll, though it is a nearby eucalyptus that scents the spring air.
Last year the German parliament offered DM3m (pounds 1m) in order to build the town a sports centre, a good-will gesture that Mayor Vallejo appreciates, although he would have preferred a formal apology.
"They can't pay with money for destroying our people," he said. "But they could say sorry, and the 60th anniversary would be a good opportunity."