The guns of Mar del Plata were one act in a national drama. On 16 September 1955, a military rebellion broke out against President Juan Domingo Peron, the towering and divisive figure who had reshaped Argentina around himself and his late wife, Eva. The rising took its grand name from its own ambitions - the Revolucion Libertadora, the Liberating Revolution - and it spread from a command post in Cordoba to the great naval base at Puerto Belgrano, whose officers seized control of the fleet. The navy, more than the army, turned against Peron. When the rebel admiral Isaac Rojas learned that an army column loyal to the president was driving south toward Puerto Belgrano and would refuel at Mar del Plata, he made a cold calculation: destroy the fuel, and you strand the column.

The order was blunt - destroy the oil and fuel tanks at Mar del Plata, with prior warning to the population. But warning a sleeping city is harder than firing on it. One commander's message turned so threatening, demanding that whole blocks along the coast be cleared, that his own flotilla captain confronted him; the man later admitted the harsh words were just an outburst. The cruiser's own artillery chief, Commander Raul Francos, argued for waiting until daylight to spare civilian lives, and the ship's commander agreed. Through the small hours the warships rolled in rain and heavy seas off the dark coast, holding fire, flashing Aldis signal lamps at one another to settle the order of attack - a strange, patient courtesy before violence, buying time for the city below to wake and run.

The cruiser ARA 9 de Julio opened fire at 7:15 in the morning. The first broadside fell short along the shore to find the range; the second struck home, and two or three fuel tanks went up in immediate explosions. Within minutes most of the eleven tanks were ablaze or destroyed. The gunnery was directed by a spotter hidden inside the besieged naval base, and for the most part the shells found their mark - though some stray rounds fell on a nearby quarry, and others from the destroyers damaged civilian houses around the port, leaving the distinctive chalet-style homes of the neighborhood scarred. The families who had ignored the warning now fled on their own, hundreds of them streaming away from a waterfront wrapped in burning oil smoke.

By 9:30 a.m. the destroyers had scattered the loyalist troops and armed Peron supporters dug in on the hills around the naval base, and rebel sailors landed from three commandeered yellow fishing boats to take the base itself. The fighting was, by the standard of what it accomplished, remarkably light. The clearest known death was its quietest: Miguel Angel Rabini, a petty officer who volunteered to stay behind at the base, took his own life in circumstances never fully explained. Press of the day reported a handful of wounded; the full human cost was never officially counted. The strategic prize, though, was enormous. Most historians credit the shelling of Mar del Plata with breaking Peron's will to fight. That same day - 19 September, the day the tanks burned - he offered his resignation and soon went into an exile that would last eighteen years.