I'm not quite qualified to explain this in detail, but there is one facet I'm familiar with. I'll lay that out and let others more knowledgeable fill in around it.

Did you ever wonder how curry became an incredibly popular part of Japanese cuisine? It didn't come directly from any other nation in Asia where curry or similar dishes were staples; instead, it came from Britain.

The year is 1870 (-ish, books I've read have given dates a year in either direction on this). Emperor Meiji was well on his path of solidifying power over his realm, restructuring the government after the abolition of the Shogunate in 1867, the end of the former government's isolationist policies, and modernizing the nation. This included the military naturally, and specifically we're looking at the navy. Meiji wanted his navy to be patterned after the greatest navy in the world, and at that time that meant the British Royal Navy (previous attempts to emulate western navies had focused on that of the Netherlands).

Enter Lt. Commander Archibald Douglas and the 34 men under him. In 1873, Douglas and his men were dispatched to Japan to oversee the restructure and training of the IJN, with Douglas spending six years as the head of the Tsukiji Naval Academy. Their mission was to remake the IJN in their own image, everything from uniforms to food. The prevailing wisdom at the time was that the on-average shorter heights and slimmer builds of the Japanese sailors was due to their diet, and that a diet containing more red meat would cause them to grow and fill out to match their British counterparts (this obviously did not happen), in addition to countering nutritional deficiencies such as beriberi (a huge problem previously, as plain white rice was the main portion of the Japanese sailors' diets, and in some cases was their entire diet).

In particular, beef curry had gained radical popularity in Britain over the past half-century, and was a regular meal in both the army and navy, who developed their own recipes to fit their ability to prepare. The British naval version of curry was even further removed from its Indian roots than the versions served in British restaurants, consisting primarily of preserved beef, root vegetables, and pre-mixed curry powder in a flour-thickened sauce (as the meat and flour both contained thiamine, this was an ideal meal to stave off beriberi). Under Douglas' direction, beef curry became a weekly meal for all IJN sailors (I've heard specifically on Fridays, but have never seen any specific proof of this).