The V weapons while technologically revolutionary did not possess the ability to force the UK to end the war. Only the U-boat force had that ability and Hitler went to war too early, with too few submarines and wasted resources on surface ships. Our sub forces strangled Japan in much the same way in 43-45.
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As an amateur historian of WW2, I have to somewhat quibble with K1052 in terms of the importance of subs in Germany and especially the Pacific theaters of war.
K1052 is somewhat correct on German subs during the 1939-42 phases of the Atlantic German phases of the war, dubbed the happy years by German submariners. As German engineering and mass production perfected fast assembly of new and faster submarines with longer range. But better sonar systems plus the convoy system allowed the allied forces to keep German sub sinking at pace with German production. But the real end to subs came with the British invention of the magnetron, a sub centimeter radar system small enough to fit on planes. And as the allied forces had gained the air advantage, subs were dumb, fat, and happy when they surfaced to charge their batteries at night. Unaware that land based planes could see them plain as day.
But in the Pacific is where K1052 is most wrong, as few Japanese or US subs had the range to operate in a 5000 mile Ocean. As the Japs based their whole strategy on knocking out the US Naval forces at Pearl Harbor. And while the Japs decremented most of the US Pacific Ocean battleships, the US carriers, had already put to sea a few days before. Leaving the USA almost defenseless to a greatly superior Japanese Navy,. As Japan had more carriers, battleships, and naval assets of all types. But no where was the disparity as great as in the quality of Japanese planes and pilot training. But after Pearl Harbor could not really press their advantage, as they were consumed with chasing out any remaining European Naval assets and capturing all the colonial assets of Southeast Asia. That would allow them the natural resources to sustain a war economy almost indefinitely. As the whole Pacific Ocean became an Japanese lake where nothing could trespass.
The US in 1942 had only one advantage, they had cracked the Japanese Naval code and learned Midway Island was the next target. As the US gambled all their carriers in a gamble to surprise a vastly superior Japanese armada, consisting of 4 carriers, the most modern battleships, plus a huge number of troop transports that should have made taking midway Island a piece of cake. The Japs struck first as they bombed and the Island and shot down and allied planes. Little aware 3 US carriers were lying in ambush to the Northwest. As the US carriers were first to detect the Japanese carriers and all three launched strikes with decidedly inferior US planes of various types in an ill co-originated attack. As the Japs shot down wave after wave of US planes with their vastly superior zero fighters until the USA got incredibly lucky. In repelling a ill fated set of torpedo bombers it pulled their zero fighters down to a low altitude, just as a set of late arriving US dive bombers found themselves over the entire four carriers at high altitude. And even then found themselves double lucky as all four Jap carriers were rearming and fueling. And soon 3 of the four Jap carriers were ablaze and sinking, and the other was badly wounded. As the Japanese invasion of midway was called off.
After that it was simply what Yamotota feared, once the war economy of the USA gained critical mass, it could out produce Japan by a wide margin, and even if the Japs still retained a descent Navy, it became worthless as the Japs could no longer obtain the oil to fuel them as the brilliant MacArthur Island hopping strategy soon found its self withing B-29 bombing range.
We can somewhat ask was an A-bomb Necessary to finish Japan off to avoid the casualties of a US invasion? If the US had waited a few months, Japan would be forced to surrender because it could no longer feed its own people who were already starving as it was.
