What is that strange bomb in the sky?

That’s what the sailors of the Italian battleship Roma must have wondered in the final moments before they died.

Naval warfare changed on Sept. 9, 1943. Dictator Benito Mussolini had been deposed, the new Italian government was abandoning a lost war and its doomed Nazi ally and the Italian fleet was sailing to Malta to surrender. But the habitually treacherous Nazis, who had always suspected their Italian allies of similar trickery, detected the Italian ships leaving port.

The Luftwaffe dispatched a force of Dornier Do-217 bombers to deal with the Italian ships.

As the bombers approached, the Italians were unsure whether the Germans meant to attack or just intimidate. They were relieved to see the German aircraft appear to drop their bombs into the ocean. Perhaps with uncharacteristic gentleness, the Germans were just firing warning shots.

But then something unexpected happened. Instead of plunging straight down into the sea, the bombs headed toward the Italian ships. One slammed into Roma’s hull, exited out the other side and exploded in the water, destroying an engine room.

A second bomb penetrated the deck into the forward magazine, where shells for the ship’s big 15-inch guns were stored. The battleship exploded, killing 1,253 members of her crew.

The age of the ship-killing missile had dawned.

The first anti-ship smart bombs, invented like so many other weapons by the dark scientists of Nazi Germany, were not just deadly. They seemed inhuman. A “Wellsian weapon from Mars,” was how one newspaper reporter described an early attack.

Smart bombs have become so common in modern warfare that we take them for granted. Yet 70 years ago, a bomb that could chase a ship seemed as exotic and frightening as the muskets of the conquistadors must have seemed to the Aztecs. The Germans “made them [the missiles] turn corners,” an Allied sailor complained.

Anti-ship guided missiles have been used for decades now. Missiles sank the Israeli destroyer Eilat in 1967 and the British destroyer Sheffield in 1982. Today, China hopes that weapons such as the DF-21D ballistic missile, with a range of a thousand miles, can sink U.S. aircraft carriers and thus neutralize American naval power in the Pacific.

But these weapons did not materialize overnight in a Beijing weapons lab. They are the fruits of Nazi research from more than 70 years ago.

A smart bomb named Fritz

The weapon that sank Roma was known by the very German name Fritz-X. It was not a powered missile but a 3,000-pound armor-piercing gravity bomb meant to be dropped from a bomber at 20,000 feet.

Battleships were armored to survive multiple bomb hits—in 1944, the Japanese super-battleship Musashi was hit by 17 bombs and 19 torpedoes before sinking. But a bomb dropped from high enough should have enough kinetic energy, imparted by gravity, to smash through thick deck armor.

The problem was hitting the battleship in the first place. High-flying bombers in the 1940s had scant chance of hitting a warship frantically weaving through the water at 30 knots. That meant aircraft had to come in low to attack, which made them easier targets for the ship’s antiaircraft guns and also robbed the bombs of kinetic energy.

The 11-foot-long Fritz-X, slung under the wing of a bomber, had radio-controlled fins that could change the munition’s glide path. A tail-mounted flare enabled the operator on the bomber to track and adjust the weapon’s course. Tests showed that 50 percent of bombs would land within five meters of the target—astounding accuracy for the 1940s.

Does this sound familiar? It should, because the concept endures in modern weapon such as America’s Joint Direct Attack Munition, a kit that makes dumb bombs smart by adding fins and satellite guidance.

The Hs 293 missile

The Fritz-X was an awesome battleship-killer, but only under the right conditions. A glide bomb has only gravity rather than a rocket motor for propulsion. The steerable fins on the Fritz-X could adjust its trajectory only slightly, meaning the bomb had to be dropped within three miles of the target.

While deadly to heavily armored warships, the armor-piercing Fritz-X was actually too much bomb for small ships. It would slice all the way through unarmored destroyers and transports and explode in the sea.

The Nazis had another weapon, a genuine anti-ship missile called the Hs 293. The 12-foot-long weapon looked like a miniature airplane with a rocket motor slung underneath.

The radio-controlled Hs 293 could be launched from 10 miles away, out of range of shipboard anti-aircraft guns. Its 2,300-pound high-explosive warhead detonated on contact with a lightly armored ship.

“In a typical deployment, the attacking aircraft would approach the target to within 12 kilometers (6 miles), then fly a parallel course in the opposite direction,” writes Martin Bollinger, author of Wizards and Warriors: The Development and Defeat of Radio Controlled Glide Bombs of the Third Reich.

“When the ship was about 45 degrees off the forward right side, the aircraft launched the HS-293,” Bollinger continues. “The Walther liquid-fueled rocket, running for 10 or 12 seconds, would accelerate to about 600 kilometers per hour (325 knots), at which point the operator had turned the missile into the target.”

“Once the rocket burned out,” Bollinger explains, “the missile continued with its forward momentum, maintaining a glide by virtue of short wings, until the operator steered it into the target.”

The electric razor missile defense

The British and Americans were gravely worried. By the fall of 1943, Allied forces had captured North Africa and Sicily, the U-boat threat was diminishing and the Luftwaffe faded before growing Allied air strength. Now the Brits and Americans could focus on the dangerous task of landing their armies on the European continent.

First they had to thwart the new German ship-killers. The Allies could mostly protect the vulnerable amphibious invasion fleets from regular German air attacks. But if German aircraft could stand off at a distance and lob bombs with pinpoint accuracy onto the soft-skinned transports and their escorts, then the Third Reich might stave off invasion.

Fortunately, a disgruntled German scientist had warned the Allies about the smart bombs in 1939, and Ultra code-breakers had intercepted German communications regarding the weapons.

The British outfitted the sloop Egret with special equipment to identify the radio frequencies used to control the German munitions. Some 13 days before Roma was sunk, Egret joined a convoy sailing within range of German bombers based in France.

As hoped, the Germans attacked the convoy with Hs 293 missiles. Unfortunately, one of the ships sunk was Egret.

The Allied landing at the southern Italian port of Salerno on Sept. 3, 1943 was a wake-up call for alliance. The Germans counterattacked and almost drove the Anglo-American troops into the sea. Gunfire from Allied warships saved the landing force … and the entire operation.

But at a terrible cost. The Luftwaffe launched more than 100 Fritz-X and Hs 293 weapons. A Fritz-X struck the famous British battleship Warspite and put the vessel out of commission for months.

Another Fritz-X hit a gun turret on the U.S. light cruiser Savannah and “penetrated through the two-inch armored surface of the turret, tore through three more decks and exploded in the ammunition handling room deep in the bowels of the ship,” Bollinger writes.

Miraculously, Savannah survived—but 197 of her crew did not. German guided weapons sank and badly damaged around a dozen ships off Salerno.

Convoys sailing the Atlantic and Mediterranean also suffered. Convoy KMF-26, whose escort included included two U.S. destroyers equipped with the first anti-missile jammers, was attacked off the Algerian coast on Nov. 26, 1943.

An Hs 293 slammed into the troop transport Rohna, carrying U.S. soldiers to India. At least 1,149 passengers and crew died in what Bollinger describes as the “greatest loss of life of U.S. service members at sea in a single ship in the history of the United States.”

It was not until the 1960s that U.S. authorities even admitted that Rohna had been sunk by a guided missile rather than conventional weapons.

Rumor spread among desperate sailors that switching on electric razors would jam the radio frequencies of the “Chase Me Charlies,” as the British called the guided munitions.

An urgent and massive anti-missile effort ensued. Ships were told to lay down smokescreens so Germans aircrews couldn’t see their targets—and to take high-speed evasive action under attack. But how could anchored transports unloading troops and supplies, or warships providing naval gunfire, maneuver at high speed?

The Allies pinned their hopes on electronic warfare, another class of modern weaponry originating in World War II. The British were already dropping aluminum foil decoys to jam German radars. Less well-known are the Allies’ intensive efforts to disrupt German anti-ship missiles.

Allied agents interrogated captured Luftwaffe aircrew. Recovery teams sifted through missile fragments from damaged ships and examined remnants of bombers left behind on airfields in Italy.

The most intensive work took place in labs across Britain and America including the U.S. Naval Research Laboratory, where scientists worked feverishly to jam the radio frequencies used by German missile controllers. operators to control the missiles.