The Imperial Japanese Navy
The Japanese navy of the day was a highly effective and very modern force, having only been created with in the last 20 years, with most of its ships being buitl with in the last 10. It consisted of 2 Deradnoughts, 1 modern and 2 2nd class battlecruisers, 10 pre-dreadnought battleships, 8 armoured cruisers, 15 protected cruisers, 6 light cruisers, around 50 destroyers, 12 submarines, numerous smaller costal and torpedo ships, and an aircraft and seaplane carrier. Most of these ships had been originaly built in European shipyards, only being constructed in Japan later. However, by 1910 only 20% of the parts needed to build these ships were comming from Europeans. The Japanese stratgey of “copy, improve, innovate” ment that by 1914 there was nearly no difference in the quality of ships comming from Japanese shipyards, as those comming from British ones. The battles against the Russians had taught the Japanese commanders the value of big gun ships, and most of the ships designed and built after this period reflect this. The battle of tsushima taught them the value of keeping their fleet concentrated and coordinated. The Japanese fleet was also the first in the world to use wireless telegraphy helping giving them an edge in intership communications and coordinations.
The greatest advantage for the Japanese fleet was that their European counter-parts were scattered and small in number, concentrating most of thie ships in European waters. The allied forces arrayed against them were small and would have been no match for a combined Japanese fleet. They were, for the most part, a mix of cruisers of various qualities, light, armoured, and protected, along with destroyers and other smaller vessles. The British pacific squadron had the largest ship on the allied side, with a battle cruiser stationed, I believe along with the few other escorting ships, in Singapore.
Japans opening strike on this force would see this, the only real allied force capable of stoping the Japanese, sunk rapidly with most likely limited Japanese losses. Also this combined fleet, re-inforced and working in conjunction with the German pacific squadron, would seek out any other large concentrations of allied warships and sink them. This would cause the Allied command in Europe, espically the British, to have to send more ships to protect its holdings and its commerical shipping, which would be at the central powers mercy in the pacific.