How New Zealand Won WWII

It could have been "The Last Great Naval Swordfight".
The result certainly changed the course of the Pacific War, and it all hinged on a little New Zealand navy corvette.
In January 1943, ferocious battles raged in the Solomon Islands. The Allied naval forces defending the Guadalcanal area included HMNZS Kiwi and sister ship HMNZS Moa. These Bird Class corvettes or minesweepers (sometimes ingloriously called trawlers) were quite small: just 51m. Heading towards them was a very large Japanese submarine, the I-1. At 98m, she dwarfed the pair.
After the Battle of Midway (June 1942), Japan had realised the Allies had cracked its military codes, so it brought its reserve codes into operation. I-1's crucial task was to deliver 20,000 reserve code books to Japanese forces in the South Pacific.
On the night of 29 January 1943, I-1 (under the command of Lt.Cdr. Eiichi Sakamoto) lay west of Honiara, near the area under Japanese control. Sakamoto managed to avoid the patrolling destroyers but, when taking one final look before surfacing, he missed seeing the small corvette Kiwi…
When the large sub broke the surface directly in front of Kiwi, its captain (Lt. Cdr. Gordon Brisdon) could not believe his eyes. The submarine's phosphorescent outline could be clearly seen in the moonlight so Kiwi dropped six depth-charges. Immediately it dropped another six and the sub was forced to remain on the surface, its electric motors disabled. Switching on its diesels, I-1 made a run for it and a surface battle ensued, the vessels exchanging gunfire...
With everyone on Kiwi’s bridge highly excited, Brisdon called out for "Full speed ahead!" to ram the sub. Considering its size, the Engineering Officer expressed doubts, but Brisdon would hear none of it. He promised the crew a week-end's leave for a successful ramming. Kiwi surged forward and struck the submarine on the port side behind the conning tower. Japanese troops in full packs emerged on deck and many jumped overboard. As Kiwi backed away, her gunners fired the 20mm bow-mounted Oerlikon gun into landing barges strapped to the sub's afterdeck. They burst into flame and lit up the area in a dull red light. During this wild melee, the I-1 gunners fired a few rounds at Kiwi but missed. In return, the New Zealanders cut down the sub's gun crew and the captain Sakamoto, leaving the navigator in command.

Kiwi's bow damage

But the sub refused to sink, so Brisdon ordered a second ramming: "Hit her again! It'll be a week's leave!" The battle raged on with reserve gunners pouring out on the sub's deck to man the guns. They scored a hit on Kiwi, earning cheers from the Japanese. The battle showed no end in sight. Battered, Kiwi made a third ramming with the captain yelling: "Once more for a fortnight in Auckland!" This encounter had Kiwi mounting the sub's deck before sliding off.
The I-1 navigator rushed inside the conning tower yelling, "Swords! Swords!" The navigator, a famous swordsman in Japan, re-emerged topside with the first lieutenant, both wielding ceremonial swords. By now, pandemonium reigned on the submarine. As Kiwi closed for another encounter, one of the swordsmen jumped towards the corvette and managed to briefly grab the railing.
At this point, the stage was set for what could have been one of the most astounding battles of World War Two: a fully-fledged swordfight on the deck of Kiwi! But it was not to be. The damaged Kiwi backed away, giving sister-ship Moa (commanded by Lt. Cdr. Peter Phipps, later to become the first NZ-born Chief of Naval Staff) a chance to take its place. In the confined shallow waters, there had not been enough maneuvering room for Moa to participate in the engagement earlier, although it illuminated the target with 'star shells'. Now, more than two hours after the first attack, it chased the sub with its gun blazing.
The submarine was taking on water and the first lieutenant tried to run it aground as the stern sank. I-1 came to rest stranded on a reef, and the sword-wielding navigator was captured by Moa's crew. The morning light revealed I-1 projecting 15m out of the water at a 45° angle. 27 Japanese sailors were dead or missing. 66 survivors had reached the shore, carrying the secret code books which they tore up and mostly destroyed…but over 200,000 pages of secret documents fell into Allied hands.
So ended what could have been one of the oddest battles of World War II, if it had been left to the Japanese navigator! Instead it hardly made the news, except in NZ of course. Unfortunately, no details are available of the riotous fortnight in Auckland! The Japs tried to destroy I-1 themselves: they'd learnt of its capture in an article written by a careless Australian journalist, and sent bombers in a week later.
The only Allied casualty of the battle was 23yr.old Acting Leading Signalman Campbell Buchanan. Throughout the fight, he shone Kiwi's searchlight and 10-inch signal lamp on the submarine, but this also made him a target for Japanese gun and small-arms fire. Mortally wounded, he remained at his post until relieved: he died two days later. Buchanan was mentioned in despatches and posthumously awarded the US Navy Cross.

Kiwi's victory parade, Auckland

Bridson was awarded the DSO and the US Navy Cross for his role in this action.
As for the captured codes, enough material remained intact for code breakers to once again decipher encrypted radio messages. One of the first major Allied successes from this was the shooting down of the plane carrying Japan's naval Commander-in Chief, Admiral Yamamoto, the mastermind behind the Pearl Harbour attack. His death (the first high-level assassination ever authorised by a US president) had an immediate demoralising effect on the Japanese Navy's morale and direction…and the outcome of the Pacific War.
NZ film-maker Geoff Murphy (Goodbye Pork Pie, The Quiet Earth, Utu) hopes one day to make a feature about Kiwi's significant but little-known contribution. His tentative but appropriate working title: "How We Won the War".