巨龙吞日（The Dragon Swallowed the Sun）

This achievement requires  满洲国 to annex  日本. May be done in conjunction with the 大清万岁（Hail to the Qing） and the 好人、坏人和怪人 achievements.

「Strategy」

This is a continuation of the 大清万岁（Hail to the Qing） achievement.

Now that  日本 is pushed out of Asia, research and build marines, naval transports and submarines and place them on the Korean port. Increase Relations with the  美国 and take the Train Marines Focus. This will give more special units and a bonus to marine research. Find out how many ships the Japanese have on the Sea of Japan. This is done by hovering over it and checking the tooltip. Build more submarines than that.  日本 will go to war with the Allies allowing  满洲国 to join their faction. Do not do it because it will allow them to enter territory under  满洲国 giving them more war score against the Japanese. Naval invade  日本 when ready. Either take the closest province near Hiroshima, or take the port north of Osaka. The port may or may not be guarded. If you take the Province near Hiroshima, Hiroshima may be guarded. Take Nagasaki if there are too many Japanese divisions. Once you take a port, increase its level so more divisions can be fielded in Japan. Tokyo and everything west of that might be enough to capitulate them. Once  日本 capitulates, Annex all of their territory. The achievement may not fire if  日本 gets puppeted by someone else: if the Allies or Soviet have a large contribution, you can pre-emptively puppet Japan and annex it through the autonomy system.

Alternate Strategy

If you're not interested in 大清万岁（Hail to the Qing）, another way to accomplish this achievement is to beeline for  日本. Turn historical focuses on, then spend the first portion of the game building up your industry and your army, through both traditional methods and the use of your focus tree. Don't pacify the bandits; after you get 法律大学, rush your way down to Bolster Nationalism and recruit the bandits.  日本 should ordinarily invest a little bit into Manchuria, and by taking the Divert Machine Tools decision repeatedly  满洲国 should be able to reach 30-40 factories by 1941; one or two dockyards to build convoys is not a bad idea either. After that, you'll want to rush down the Mission To Germany branch before  德国 recalls Von Falkenhausen, as this will be worth 3 factories, +1 planning skill on every leader, some free tanks, and an okay general, making this superior to the  苏联 tree; but this is not required. While all of the above is taking place, ensure that you research and begin training paratroopers, as well as building transport aircraft which are available at the beginning of the game. You don't need a ton but you can easily get to 8 paratrooper divisions before 1941, which will make the following steps easier.

Whether you accept or reject the Japanese call to arms against  中国 is irrelevant to this strategy; either way, your units are going to sit the battle out until 1941, while you train up an army of approximately 80-90 divisions. You'll probably run out of worthwhile focuses and that's okay, because the extra political power is useful for decisions, laws, and appointing members of your government. As a subject of  日本 you automatically have 100% intelligence on them; what you want to watch out for is Strike the Southern Road. As soon as you see  日本 begin that focus, you will begin the 独立战争 focus. When the war starts, assign one army of 24 divisions to conquer Korea, two armies of close to 24 divisions each to get as far into mainland  中国 as you can, a small army of 8 divisions to take Japanese Dalian, and your paratrooper army assisting in Korea. If the Japanese have any units stationed on the border with the  苏联, you'll have to divert your post-conquest Dalian army and your paratrooper army to mop those out-of-supply units up, but you're in no hurry; they won't get far. You should encounter virtually no resistance anywhere except in mainland  中国. Once you have conquered most of South Korea, build and prioritize an airbase there, then quickly deploy all of your planes there; you should have been gifted a few fighters along with the transports you built. Use those planes to launch a quick paratrooper assault on Nagasaki, which will be lightly defended; any spare paratroopers can secure the island of Kyushu and some bridgeheads on Honshu and Shikoku. Once you secure the port of Nagasaki, ship over the 24 division army from Korea and begin your conquest of  日本; with  日本's focus divided between  中国 and the  菲律宾, there should be few if any divisions remaining to defend the home islands. Any stubborn resistance you encounter can be broken by the paratroopers, by dropping them behind enemy lines and cutting enemy divisions off from supply.  日本 should fall easily. At the peace conference, because you timed your war with  日本 to limit the involvement of the  英国 and the  美国, your only competition for Japanese territories will be  中国; but  中国 will focus on Chinese territory and then bow out of the peace conference, leaving you to race the  英国 and the  美国 for the Japanese territories you need for the achievement; and neither should have enough involvement to beat you to  日本, especially since they'll focus on releasing Cambodia and Laos first.

At this point, you could pursue 大清万岁（Hail to the Qing） if you wished. Since  日本 capitulated to you, you'll need to rush your Japanese armies back to mainland  中国 to try and hold down the empty Japanese front lines, while you use the newly captured Japanese equipment to rapidly train up an army large enough to beat  中国.