Beginning of the war in the Pacific came unexpectedly, at least for some people. Attention was on Europe, where war had been raging for two years. Poland had been invaded by Germany and USSR in September 1939., and USSR invaded Finland in November of the same year. After that, Germany conquered country after country – with Denmark, Norway, Netherlands, Luxembourg, Belgium, France, Albania, Yugoslavia and Greece all falling in short order. In Asia, the war between Japan and China was already old news.
The war continued on. Air campaign over Britain captured and kept attention of the public. Even more so did the war in the North Atlantic, employing significant resources on both sides, as both knew the naval campaign was a key to either maintaining or neutralizing Britain. Stakes were increased even further when Axis powers invaded the Soviet Union. Massive expansion of war saw millions more troops thrown into combat, and millions of people were displaced or saw their homes destroyed. Soon, Leningrad was surrounded and Moscow was expecting an attack.
It is thus not surprising that nobody had cared what was happening in Asia. Eastern Asia and Pacific Ocean seemed calm: Japan had taken some areas of China, but they soon stopped with no plans for new advances evident. All of this, however, was soon to change.
Imperial Japanese Navy was, in 1941., third strongest navy in the world. Its core were 10 battleships. While over 20 years of age – as was the case in all other major navies – these ships had received extensive reconstructions and modernizations. Four of them had a relatively high speed of 26 knots, having been originally constructed as battlecruisers. Most powerful units were battleships Nagato and Mutsu, which displaced 33 000 tons as constructed but by 1941. their standard displacement had increased considerably, to maybe 39 000 tons. They had speed of 25 knots post-reconstruction, with range of 5 500 nautical miles at 16 knots, and armament of eight 410 mm guns. Under construction were new battleships Yamato and Musashi, which displaced 70 000 tons with speed of 27 knots, range of 7 200 nmi at 16 knots, and armament of nine 460 mm guns.
Most important element of the Japanese Navy were aircraft carriers. Japanese naval command had placed particular emphasis on development of the naval aviation, and was the first in history to field carriers as a centerpiece of its fleets. Despite this, development of Yamato class shows that it did not wholly abandon the idea of battleship as a decisive naval unit. At start of the war, Japanese fleet had 13 aircraft carriers, and two were about to be finished. Of those, seven were actually bases for hydroplanes. As such, Japan only had six fleet aircraft carriers, plus two under construction. Most powerful operational units were Akagi and Kaga, carrying 66 and 72 aircraft, respectively. Other ships were smaller, and carrying 30 to 40 planes. Ships under construction, Zuikaku and Shokaku, were even larger, capable of carrying 72 aircraft each.
Japanese navy had a very powerful cruiser force. This was a consequence of the Washington Naval Conference, which had limited the displacement and armament of cruisers, but did not limit their quantity. Thus, Japan forcibly built cruisers and by 1939. had a very powerful force of 12 heavy and 28 light cruisers. Aside from those, Japanese Navy had 96 large and 40 small destroyers, 36 large and 22 small submarines, and a large number of auxilliary ships. In total, Japanese navy had almost 400 warships displacing 1 270 000 tons.
