Falling bombs and the rise of a nation : Catching submarines
A little while ago I announced a series I would do about the bombing of Darwin, Australia. I've done a couple posts so far and it's time for part three. You can find the other two by following the links part one and part two here.
Today I want to talk about the anti-submarine boom-net which was erected across Darwin harbour, obviously to protect shipping from the submarine and torpedo threat. src
Darwin wasn't a stranger to the submarine threat as enemy vessels were plying the waters long before World War Two began and certainly, since war was declared, the threat increased. The need to protect allied shipping within the harbour was real and so work on the anti-submarine net began around 1941 and it was operational by 1942.
The boom-net was a 5.6 kilometre net spanning the 3 kilometre harbour entry - It had to be that long so it could snake around and be flexible with the tides which in the area are 8 to 10 metre tides (8.7 to 10.9 yards). 5.6km is 3.4 miles and 3km is 1.86 miles in case you're wondering.
The net was constructed down in Newcastle, New South Wales and was installed and operated by young soldiers, not seasoned ones as they were overseas in various theatres of war around the globe. Those young soldiers monitored it 24 hours a day. Its construction and installation was a monumental effort and feat of engineering brilliance considering the huge tide in the area, however it was essential to protect the port, a strategic mooring for allied shipping.
The installation required incredibly heavy anchor-points on the east and west sides of the harbour with high-tensile steel rope cable running between. The ends ran through almost 8 metre high towers at each side and along its length across the harbour mouth were steel floats, cylindrical in shape, which kept the cable-span afloat.
From the floating surface-cable a heavy steel mesh netting hung reaching all the way to the bottom of the sea-bed, anchored/tethered to massive concrete blocks so it stayed in place. Naturally enemy submarines could not penetrate this heavy cable-net and so the harbour, the allied vessels, were protected.
It was operated by six boom-winch-ships, around the clock. Each float had two ships positioned there and when allied shipping needed to cross the boom-net they would winch a section of netting down allowing the ship to pass over before winching it back up once more.
The below diagram offers some perspective on how the opening and closing operation worked. src
The boom-net, manufacture, installation and operation was a massive undertaking and fortunately all that effort paid off with zero enemy submarines entering the harbour. Of course, the boom-net didn't prevent them from laying sea-mines and torpedoing shipping outside the net but losing that harbour, by having ships sunk within it, would have proven catastrophic to the allies plans.
On the 21st or 20th January 1942 the Royal Australian Navy (RAN) Corvette, HMAS Deloraine, fired upon and sunk an Imperial Navy submarine, the I-124, outside of Darwin Harbour. It was one of at least three (probably four) submarines laying mines and torpedoing allied shipping in the area. The I-124 went down with all hands on board and lies on the bottom, untouched, outside the inlet to Darwin Harbour to this day; A watery grave for the poor brave souls within.
Coordiniates of the Sensuikan class Japanese submarine I-124 are:
12 degrees 07'12.320" S 130 degrees 06'23.619"E at the reasonably shallow depth of only 30.4 metres (100 feet). It is protected by a government-enforced and monitored exclusion zone of 1 kilometre. Trying to get to it would go badly for a person. Exactly why it is monitored to this day is a source for conjecture, but I may cover that in another post so you'll have to wait for it.
Interestingly, on the 19th February 1942, when the bombing raids commenced the ships that operated the boom-net were the first to be attacked. If the enemy attack had been an air and sea operation, and the boom-net didn't exist, the attacks would have had a much more catastrophic effect upon Australia and her allies. The harbour allowed limited movement for shipping and with 49 allied vessels at harbour that day...A couple of submarines in the harbour would have made a massive difference to the severity of the raids. Thanks to the boom-net that didn't happen.
The boom-net is thought to have been removed around 1947 although the massive winch and other machinery remained in place for much longer.
There's nothing to see of the boom net these days, I've been there and looked, although the winch used to remove and maintain sections has been restored and is situated at the Darwin Military Museum for all to see. It's a big thing for sure. Imagine the power required to haul that length of cable!
Much of the facts around what happened in Darwin in World War Two is classified, and much was destroyed. Fortunately a lot still survives and I find it fascinating to discover as many don't know anything about the extensive bombing raids over Australia. When we were in Darwin we toured these places where, even now, signs of the attack and devastation can be found.
Darwin is still very much a military installation and again, much about it is shrouded in secrecy, although I think it's cool we can look back and learn about what happened so many years ago, the stories around it, the hero's, victims and villains, and events that played out in the defence of this fine country of mine.
Thanks for reading. Stay tuned for part four.
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