The 15th of February 1942, Singapore. The most powerful British fortress east of Suez, surrenders in less than a week of serious fighting. 85,000 soldiers, British, Indian, Australian, lay down their arms to a Japanese force less than half their size. The great guns of the naval base are pointed out to sea.
Nobody has thought to turn them around. The invasion that was never supposed to happen has already happened. And now there is nothing between the Japanese army and the continent of Australia. In Canra, Prime Minister John Cirten does not mince the words. The fall of Singapore, he tells The Nation over the radio, opens the battle for Australia.
He has already turned away from Britain in print, writing in the Melbourne Herald barely 6 weeks earlier, that Australia looks to America, free of any pangs as to our traditional links or kinship with the United Kingdom. The Empire’s promise, the Singapore strategy, is rubble. Darwin is bombed.
4 days later, Japanese aircraft appear over broom. In the deep files of Imperial General Headquarters in Tokyo, a naval proposal to invade the Australian continent is under active consideration. Australians do not know it will be rejected. They prepare for the worst. Here is the thing they do not know yet.
Or rather, the thing that makes this story extraordinary. Before Singapore has even fallen, before the bombs fall on Darwin, a small team of engineers in New South Wales is already building Australia’s first tank. Not importing one, not borrowing a design, building one from nothing in a country that has never made a tank in its history.
And the machine they will eventually produce, upged, re-engineed, renamed the Thunderbolt, will be the most capable cruiser tank in the Pacific Theater. It will never fire a single shot in anger. To understand why Australia built it, you need to understand the particular kind of loneliness that fell on the country. In the winter of 1940, Britain was fighting for its own life in the skies over Kent.
every tank rolling out of a British factory was desperately needed on home soil. In North Africa, in the Middle East, there were none to spare for a dominion 12,000 mi away. And yet, general staff planners in Melbourne could read a map. Japan was mobilizing. The Pacific was heating. If war came south, Australia would face it with a handful of obsolete Bren carriers, some light tanks, Mark 6, and whatever the Americans might eventually get around to sending. That was not a plan.
That was a prayer. On the 12th of June 1940, Prime Minister Robert Menses convened a meeting with the director general of munitions, Essen Lewis, and the chief of the general staff. The agenda was blunt. Australia needed to build its own tank. By November, the general staff had issued a formal specification.
16 to 20 tons, a 2 lb gun, 50 mm of armor, 30 mph, a range of 150 mi, crew of five. They wanted deliveries to begin by July 1941 at 70 vehicles a week. It was a wildly optimistic timetable for a country with no tank industry, no tank designers, and no tankrade steel production to speak of. They said it anyway.
The man brought in to make it real was a British officer on succtories where the new American M3 medium was being developed. He arrived in December 1940 carrying notes. The engine and drivetrain logic of the M3 would underpin the lower hull. The upper hull and turret would be styled on the British Crusader. A French connection entered through Robert Perry, an engineer who had been working in Japan for the French government, fled the collapse of the Pacific situation and made his way to Australia, bringing with him an intimate knowledge of the Hotchkiss suspension system used on pre-war French tanks, which Watson’s team adapted and found much superior to the American pattern they had originally planned. The result was the Sentinel Australian Cruiser Mark1, and the engineering inside it was unlike anything built before. Because Australian welding technology in 1941 could not reliably join the type of thick, high hardness armor plate the hull required, the designers cast the
entire upper hole as a single piece. The first tank in the world with a one piece cast hull, the turret was cast in one piece, too. The armor itself, designated a BP4, was a locally developed alloy, substituting zuconium for nickel because Australia had nickel in the ground, but not the infrastructure to refine it fast enough.
And for the engine, there was nothing suitable in the country at all. The preferred radial aircraft engines were spoken for by the Air Force. So, the engineers took three Cadillac V8 automobile engines and arranged them in a triangular configuration feeding a common gearbox. Three car engines bolted together in a clover leaf producing 330 horsepower. It worked.
If you find that channel bookmark useful and want to keep following stories like this one, there’s a subscribe button below this video. It takes 1 second and it genuinely helps us keep going. The first prototype rolled out of the New South Wales government railways workshops at Chalora in January 1942, the same month the Japanese were advancing down the Malay Peninsula.
The same month the last reinforcements were sailing into Singapore. It was given a name, Sentinel. 65 production vehicles followed, completed between the middle of 1942 and June of 43. They were used for evaluation and crew training on Australian soil. They never left, but even as the Sentinels were rolling out of Julora, the men designing them were already making them obsolete.
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The two pounder gun the First Sentinel carried was, in the words of the Australian officers who evaluated it, a pop gun, a peashooter. It had been adequate in 1940 against the tanks it might have faced then. By 1942 in North Africa, British crews with two pounders were watching their rounds bounce off the frontal armor of Panzer 4s and Tiger.
The problem was universal. The Australians identified it immediately. They began looking for the largest gun they could fit inside the turret ring. The six pounder was unavailable. The 17 pounder, Britain’s best anti-tank gun, was barely in production, and none had reached Australia.
What Australia did have in large numbers was the 25p pounder gun howitzer, the standard British and Commonwealth field artillery piece, firing an 87.6 mm shell with a 20 lb armor-piercing shot and heavy explosive capability alike. In June 1942, engineers fitted a modified 25p pounder to the second development hull and test fired it. The recoil was manageable.
The accuracy inside the turret was, in the written verdict of the director of artillery, superior to that of a field mounting. The noise, he wrote, was similar to that of a big air rifle. It worked better than anyone expected. Field marshal Sir Thomas Blamey, commander-in-chief of Australian forces, formally recommended the upg variant to the war cabinet in July 1942.
The new design deleted the whole machine gun and its gunner. The 25 pounder ammunition was bulkier and something had to give, reducing the crew from 5 to four. The Glacis was re-angled. The engine bay was redesigned around a more compact arrangement of the three Cadillac units, now fitted radially around a common crank case by Robert Perry himself, producing 397 horsepower.
From a 24-cylinder power plant, displacing 17 L. The engineers called it the Pererry Cadillac. It was among the strangest power plants ever fitted to a combat vehicle. This machine was given a new name, the Thunderbolt Australian Cruiser Mark III. The single completed Thunderbolt, serial number 80066, was delivered to the Australian Army on the 12th of June, 1943.
A testing officer drove it, fired its gun, evaluated its handling, and wrote in his report that production models would be a good fighting vehicle with excellent armorament. Production was authorized. Around 150 hulls were cast. The first batch of roughly 25 trial tanks was under assembly at Chulora.
An order for a substantial further production run was on the table. And then 6 weeks later, the program was cancelled. The reason was not failure. The Thunderbolt had not been rejected on technical grounds. The reason was that the war had moved. The Coral Sea and Midway fought in May and June of 1942 had broken Japanese carrier power.
Guadal Canal and Cakakota had stopped the Southward advance. By December 1942, 757 M3 Grant and Lee medium tanks had arrived in Australia from the United States, equipping the armored division that had been raised to defend the mainland against an invasion that was no longer coming. The first Australian armored division was disbanded in September 1943.
There was nothing for a fast cruiser tank to do in the jungle fighting of New Guinea. The Matilda 2, a slower and older design, was better suited to the terrain and was already available in numbers. The government decided the factories at Cholora were more urgently needed building railway locomotives to move American equipment.
In July 1943, the order came down to stop. Every hull under assembly was broken up for scrap. The 150 cast hulls awaiting fitting were melted down or sold off. The 65 production sentinels went into storage. Their only operational deployment, if one can call it that, came in 1944 when the film director Charles Chau borrowed a number of them for a war picture called the rats of Tbrook.
Painted with iron crosses and fitted with mock German cupillas, the Sentinels drove through the Krenula sand hills pretending to be panzas, they were better equipped to fight actual panzas than their role suggested. Nobody in the film knew that. Compare the Thunderbolt to what it would have faced.
The Panza 4 hours FH, the primary German medium tank of the same period, carried 75 mm of frontal armor and an effective high velocity 75 mm gun. The Thunderbolts 25 pounder could penetrate it at combat range. The Sentinel’s armor of 65 mm was comparable against the M4 Sherman, then flooding into Allied infantries.
The comparison is closer than the Sherman’s reputation suggests. The Thunderbolts armament was at least its equal for versatility, and the singlepiece cast hull was structurally superior to the Sherman’s welded construction. Nicholas Moran, the American tank historian who crawled through the surviving Sentinel at Bovington, judged it ergonomically poor and noted that by mid 1942, it was already a little dated by European standards.
That is a fair verdict, but it was built for a Pacific war against Japanese armor that was lighter and less well protected than anything in North Africa. And for that specific threat, it would have been more than adequate. What happened to the Thunderbolt serial 8066, the only complete example ever built, survived.
It sits today in the Trielor Technology Center of the Australian War Memorial in Canra out of general public view. On its front hull, there is a brass plaque. The Bonathan family of Adelaide donated £25,000 toward the production of a cruiser tank. The tank they funded was the only one of its kind.
Three production sentinels also survive. One at the tank museum in Bovington in England, sent for British evaluation and never returned. One at the Royal Australian Armored Corps Tank Museum at Puka Punil in Victoria, still a runner and two partial examples reassembled from salvaged components at the Australian Armor and Artillery Museum in Canes.
Back in the Chalora workshops on the 12th of June 1943, the test driver climbs out of serial 8066 and hands in his report, a good fighting vehicle with excellent arament. Outside, Australia is building locomotives. The invasion fear has passed. The tank that Fear produced, the most capable cruiser in the Pacific, built by railway workers and Cadillac engines, and a French engineer who had nowhere else to go, is about to be told it is no longer needed.
It will never be pointed at an enemy. It will never fire a shot in anger. It will spend the next 80 years in a storage facility in Canra. One tank alone named Thunderbolt, waiting for a war that never came. Australia built it anyway. That is the part that deserves to be remembered.
