Today marks 80 years since a now-famous raid struck the heart of Germany's operations during World War II. But at the time, the mission was so secretive that even the crews weren't told their targets until the night before.
On May 16, 1943, aircrews from Australia, Britain, Canada, America and New Zealand were hand-picked to fly over and bomb three dams in Germany's Ruhr Valley.
Operation Chastise — now known as the Dambusters Raid — saw 19 heavy bomber planes attempt not just to drop bombs, but to bounce them along the water and behind each dam, where they would sink before exploding.
For the plan to work, the pilots had to fly less than 20 metres above the water at a ground speed of 370 kilometres per hour, into what those who made it back described as "hell".
"Everything had to be done at night in darkness," said Shane Casey, curator at the Australian War Memorial.
"You had German anti-aircraft artillery firing at the aircraft from both sides."
Flight Lieutenant Harold "Micky" Martin, one of 13 Australians chosen for No 617 Squadron RAF — otherwise known as the Dambusters squadron — after the war told of the "trouble" that struck when he was targeting Möhne dam.
"We were flying low and suddenly we were picked up by searchlights," he said.
"We were hit in the starboard outer petrol tank, which fortunately didn't explode, but we had to get out of the range of the defences.
"After five of us all together had dropped our mines, we saw a great wall of water shoot out horizontally from the dam wall.
"When we got home, the wing commander informed us that so clearly were we illuminated, he could distinguish the squadron markings on the side of our aircraft."
Of the 13 Aussies picked from the Dambusters squadron, two were killed in the operation and one became a prisoner of war.
'Hit right at the heart of Germany'
The day after the mission, King George VI visited the squadron to congratulate the Dambusters, and later all were invited to Buckingham Palace to receive military honours for flying skill and bravery.
Lachlan Grant, senior historian at the Australian War Memorial, said the raid gave a morale boost to war-weary Britain and its allies.
"The Dambusters Raid happened at a really important time in the war for the Allies," he said.
"Things hadn't been going well up through 1942, and 1943 is a real turning-point year.
"The Dambusters Raid gave Britain and the Allies great confidence that they could hit right at the heart of Germany."
The mission was so pivotal that in 1955 the raid was also immortalised on the silver screen in the movie The Dam Busters.
Mr Grant said the three dams in Germany's Ruhr Valley area that were targeted were essential to Germany's war effort, and their destruction was significant.
"The water in the dams helped power the factories to produce steel for the German war industry. 100 tonnes of water produced 1 tonne of steel," he said.
"The amount of water that was released from the dam was 330 gigalitres of water — that's more than half of the water in all of Sydney Harbour."
War Memorial to display historic models used to plan raids
Because the targets of the mission were so secret, aircrews weren't told they were attacking dams until the night before the raid.
With just hours to get ready for the raid, the Royal Air Force provided the crews with scale models of the dams to help them prepare.
"The pilots would have been clustered around these models looking at the various approaches, the landmarks," War Memorial curator Shane Casey said.
"[They would be] making sure they knew they were able to differentiate one dam from another, and what it would have looked like from a particular height."
Mr Casey said the models were very accurate even by today's standards.
"If you compare our models with, for example, Google Earth images of them taken today, there's very little change," he said.
"You can easily see all the roads that are marked on those maps."
Two of those models will soon be viewable to the public for the first time since the end of the war.
The models will be displayed in Anzac Hall at the Australian War Memorial once its current renovations are complete.
