A Nazi attack on an ally’s warships introduced the world to a weapon that militaries still love today

• In September 1943, the Germans launched their erstwhile Italian allies with an attack on their warships.
• To the surprise of the Italians, the bombs turned and glided toward the warships as they tried to evade.
• They were one of the world's first precision-guided munitions – weapons that militaries still rely on today.
• See more stories on Insider's business page.

In the early hours of September 9, 1943, 14 ships of the Italian Navy sailed south from their bases in western Italy.

The force, made up of the battleships Italia (formerly Littorio), Vittorio Veneto, and Roma, as well as three cruisers and eight destroyers, had originally planned to attack the Allies' Salerno invasion force. They were instead ordered to Sardinia to comply with the terms of Italy's armistice with the Allies, which had been announced the day before.

Enraged at Italy's surrender and worried the warships could be used against them, the Germans attempted to sink them.

By the afternoon, six Dornier Do 217 medium bombers found the flotilla. They climbed to over 18,000 feet and dropped their payloads.

To the complete shock of the Italians, the bombs actually turned and began gliding toward the battleships as they attempted to evade.

They were Fritz X radio-guided bombs - one of the world's first precision-guided munitions.

Allied intelligence knew about the weapons, but it wasn't until the September 9 attack that their destructive power became fully apparent. By the end of the day, warfare had changed forever.

The weapons

Germany had two types of precision-guided munitions by 1943: the Henschel Hs 293 and the Fritz X. Both had the Kehl-Straßburg manual command to line-of-sight radio control link, which allowed a bombardier to steer the munition into its target.

The Hs 293 was 12 feet long and 10 feet wide and looked like a small winged aircraft. It carried a 650-pound warhead and was powered by a single rocket engine with 10 to 12 seconds' worth of fuel. The bomb could reach speeds around 700 feet per second and travel about 5 miles to its target.

The Fritz X was less sophisticated, as it relied on gravity to reach its target from a range of 3 miles. But it was far more powerful. The 11-foot long and 4-foot-wide bomb had a 710-pound warhead and a reinforced nose that, combined with its speed of 1,100 feet per second, could punch through a battleship's armored hull.

The Fritz X had four centrally mounted fins and a radio antenna in its tail, allowing a bombardier to move the radio-controlled spoilers to change pitch and direction. It also had a gyroscope for roll stabilization and a flare at the tail so the bombardier could track it while in flight.

Both bombs were dropped from Dornier Do 217 medium bombers at high altitudes, sometimes as high as 20,000 feet - well out of the range of most anti-aircraft guns. Designed as anti-ship weapons, the Hs 293 was meant to destroy cargo ships, while the Fritz X was for use against warships.

Their debut

The Hs 293 made its combat debut on August 27 in the Bay of Biscay, where it was used to sink HMS Egret and damage HMCS Athabaskan, both destroyers.

On September 9, The Italians were unable to shoot down the Dornier Do 217s, which were out of the range of their anti-aircraft guns. The bombers continued flying straight after releasing their Fritz Xs - odd behavior even if they were out of range.

Seconds after the first Fritz X was released, it exploded underwater near Italia, significantly damaging its rudder.

Roma was not so lucky. It was hit by a Fritz X just aft of amidships. The bomb ripped clean through the hull and detonated under the keel, flooding the boiler rooms, an engine room, and knocking out two of its four propeller shafts.

Roma was on fire and losing speed when it was hit by another Fritz X seven minutes later. That bomb detonated in the forward engine room and ignited the forward magazine. The ensuing explosion blew a gun turret clean off the ship and caused it to capsize.

Roma broke in half as it sank, killing 1,393 sailors, including its captain, Adone Del Cima, and Vice Adm. Carlo Bergamini, the fleet commander. Italia and the other ships limped to Malta.

Roma was not the only victim of the Fritz X. In the weeks that followed, the bombs seriously damaged the light cruisers USS Savannah, killing 197 crewmen, and HMS Uganda, killing 16 crewmen, at Salerno, putting the ships out of commission for months.

USS Philadelphia was also damaged, as was the legendary battleship HMS Warspite.

Hs 293s also took a terrible toll, sinking dozens of ships. On November 26, an Hs 293 sank the troop ship HMT Rohna, killing 1,149 men, including 1,050 US troops. It was the US's single largest loss of life at sea due to enemy action.

A lasting legacy

Ultimately, neither the Fritz X or the Hs 293 saved Germany from the Allied navies.

Allied pilots learned that the Dornier Do 217s dropping the bombs had to continue flying steady and level to maintain a radio connection with the bomb, so they attacked the German bombers whenever they could to break the bombardier's line of sight and concentration.

The Allies also eventually developed jamming countermeasures, but the Fritz X and the Hs 293 revolutionized warfare.

Since their first appearance in 1943, precision-guided weapons have advanced considerably. They now no longer need to be guided by an operator and can travel long distances with massive payloads. They have become the weapon of choice for the US in recent decades, especially in counterinsurgency operations.

So many bombs and missiles were used during the first 15 months of the campaign against ISIS that the US Air Force was "expending munitions faster than we can replenish them," the Air Force chief of staff said at the time.

Over the past five years, the Defense Department has spent between $3 billion and $5 billion annually on precision-guided munitions, and Russia's and China's use of anti-access/area denial systems has led the Pentagon to argue it needs longer-range precision munitions to overcome the threat they pose, according to the Congressional Research Service.

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