No. Japan had almost no capability to continue waging war. In fact, strangled by the American blockade, Japan was tottering on the brink of collapse. Experts both then and since believed that the combined pressure of the Soviet entry, the relentless blockade (and usually, the conventional aerial bombardment campaign) would have compelled Japan to surrender. The only real question is when.
There is no real doubt that Japan was essentially defeated by 1945. The Japanese military had no means of countering either the Red Army or Allied bombers. Both of these are commonly cited as factors in speeding up a Japanese surrender, but more importantly, as an island nation dependent on the sea lanes for basic survival, Japan was doomed by her disastrous naval defeats.
Shortly after the war ended, the United States Strategic Bombing Survey undertook an investigation of the Japanese leadership in the last months of the war. They concluded that:
Based on a detailed investigation of all the facts, and supported by the testimony of the surviving Japanese leaders involved, it is the Survey's opinion that certainly prior to 31 December 1945, and in all probability prior to 1 November 1945, Japan would have surrendered even if the atomic bombs had not been dropped, even if Russia had not entered the war, and even if no invasion had been planned or contemplated.
Now, the Survey can certainly be accused of overstating their case here. Japan could well have lasted into 1946. However, it is a virtual certainty that Japan would have collapsed eventually due to the blockade alone. The rice harvest in 1945 was disastrous - some 40% short of normal levels. Japan was heavily reliant on imports even during the best of times, but that option was no longer available by 1945. A cabinet report, reproduced in the Survey's findings, bleakly states:
The food situation has grown worse and crisis will be reached by the end of this year. The people will have to get along on an absolute minimum of rice and salt required for subsistence.
Tellingly, even after the war Japan tethered on the brink of starvation for several years. Despite renewed access to imports and the massive logistical support of the Americans, Japan still could not adequately feed itself in a time of peace. Had the blockade kept up (not to mention Soviet invasion and Allied bombing campaigns), the picture would have been far more bleak.
1945 produced the worst harvest in Japan for a generation ... before 1942, Korea, Taiwan and China had provided some 31 per cent of rice imports, 92 per cent of sugar and 25 per cent of salt.
- Pike, Francis. Empires at War: a Short History of Modern Asia Since World War II. IB Tauris, 2011.
While Allied leadership did not know the precise extent of Japanese privations, the overall picture was clear. For example, Admiral Earnest King, the American Chief of Naval Operations, was convinced that the Navy would have starved Japan into surrendering.
The President in giving his approval for these [atomic] attacks appeared to believe that many thousands of American troops would be killed in invading Japan, and in this he was entirely correct; but King felt, as he had pointed out many times, that the dilemma was an unnecessary one, for had we been willing to wait, the effective naval blockade would, in the course of time, have starved the Japanese into submission through lack of oil, rice, medicines, and other essential materials.
- King, Ernest; Whitehill, Walter Muir. Fleet Admiral King: A Naval Record. New York City: W. W. Norton & Company, 1952.
The fact is, by 1945, Japan was on its last legs. Its cities were reduced to ashes, its economy ruined, and basic necessities for both war and civilian livelihood were almost depleted.
By mid-1945, largely because of America naval operations, Japan's merchant fleet had been reduced to about 10 percent of its prewar size, its oil supplies cut to under 3 percent of the prewar peak, most imports of foodstuffs, oil and other materials blocked, and Japan's economy was in shambles. Food supplies had perilously dwindled, with sharp cuts in food rations in 1944 and again in 1945.
- Hixson, Walter L. The American Experience in World War II: : The Atomic Bomb in History and Memory. Vol. 7. New York: Routledge, 2003.
Even without the conventional bombing, Japanese industrial capacity had virtually collapsed simply due to the lack of natural resources. Japan could neither feed itself nor equip its armies to fight, and with access to the outside world cut off by extensive mines and submarine warfare, there was no realistic way it could rebuild.
[B]y the summe rof 1945 output from Japan's factories was in free-fall across all sectors. Aluminium production fell to 9 percent of peak output while steel and oil refining fell to 15 percent. Monthly aircraft (mainly kamikaze) production, whose output the Japanese government sought to maintain at the cost of everything else, still fell by over 40 percent between 1944 and 1945 ... the mining of Japan's seaways by B-29s, which cut off the import of raw materials and involved no loss of civilian life, was just as effective as urban bombing in reducing Japan's industrial output.
- Pike, Francis. Hirohito's War: The Pacific War, 1941-1945. Bloomsbury, 2015.
It is popular to claim that Japan would somehow fight on due to their mythical fanaticism. Aside from smacking of racism, such claims ignore the very real fact that Japan did in fact surrender rather than fight to the death. Ultimately, Japan by mid-1945 was a thoroughly defeated nation that would soon be incapable of feeding itself, much less equip its armies for war.
Japan's situation was manifestly incomparable to British case.
Britain was fed by the whole of her empire and the United States. Japan's overseas conquests were either lost or rapidly being overrun. Britain was supplied by a huge merchant marine and the shipbuilding capabilities of the Free World. Japan's merchant marine was in the bottom of the Pacific. The Royal Navy was supreme in the open seas and could keep Britain's lifelines open. The Imperial Japanese Navy had virtually ceased to exist.
Take the differences in British and Japanese merchant marine for example. By the war's end, Japan's merchant marine had been reduced to less than 1.5 million gross tonnes, barely a quarter of its prewar strength. In contrast, Britain commanded a Merchant Navy of 15 million gross tonnes while a staggering 40 million sailed under the American flag.