Where are non-Japanese contributions to the war? I realize that the Yamato crew has to be Japanese because it was so in the original series, and they found a way to justify it in-universe with the near impossibility to move people and material from a part of the world to the other (thus the Yamato having to be built under the old warship's relic for camouflage with Japanese resources and crewed with Japanese men), but this series makes a big deal of the Cosmo Force depending from the United Nations, yet during Operation M all the ships mentioned (Kirishima, Yukikaze and Izumo) have obviously Japanese names (Kirishima being the name of a Japanese volcano with a city and a battleship sank at Guadalcanal in 1942 named after it, Yukikaze being a typical name for Japanese destroyers until the end of World War II, and Izumo being an ancient Japanese city with a cruiser sank in 1945 named after it), and the Yukikaze was stated to be an Isokaze-class destroyer (Isokaze was another widely used name for Japanese destroyers, with the Isokaze-class of four ships being in service from 1916 to 1936 and another ship of that name being sunk with the Yamato). Was it too difficult to mention a ship named Nelson for the British, a Monitor for the Americans, or a Prinz Eugen for the Germans, Austrians and Italians at the same time (the Prinz Eugen ships being named after an Italian general who fought for the Hapsburgs, Eugenio di Savoia), or to say that the Yukikaze was a La Combattante-class destroyer (named after French ships with the added bonus that the name means 'the fighting one')?
A bit of Wild Mass Guessing, it may be that the Japanese contributions to the Cosmo Forces are all that's left. Okita is mentioned as the Hero of the Second Battle of Mars and other engagements and that's more for getting the forces under his command out intact than any sort of actually success. For staging Operation M, they may have had the largest force left. As for the class names, they could be the name of the class used by Japanese forces and the same ships used by other branches of the Cosmo Force use different names (and that's assuming each branch isn't responsible for designing and building their own ships).
Perhaps true but another possible explanation is that if the UN Space Forces are organized anything like today's UN operations, then each nation's forces are organized independently. But if THAT were the reason, then why was the Japanese force assigned Operation M? In the WMG section, it is postulated that the various nations of earth each began building their own battleships designed to use the Wave Motion Core being sent by Iscandar. The first ship to be completed would get the core and the mission to Iscandar while the other ships would be completed with cores copied from the original. But in order to ensure that the warp core reached Earth unobserved, Operation M was drawn up. The operation would require a major commitment but there is the oft overlooked fact that even if the Yamato plan succeeded, there would still be a need to preserve a fleet in being to prevent the Gamilons to simply move in and finish off Earth while Yamato was away. Assume that the Japanese, American, Russian, Chinese, European Commonwealth, and the British Fleets represent the main strength of UN forces. The likelihood of winning at Pluto without horrendous casualties was virtually nil. The fleet dispatched to Pluto was going to be a write-off. Therefore the commitment of Japanese forces to Operation M was the price Japan paid for getting their Battleship up first and getting the honor of the mission to Iscandar. The other surviving fleets would have to defend Earth in the interim while Yamato was away and until the other new battleships: Arizona, Borodino, Bismarck, Andromeda, and Prince of Wales could be completed. Considering that most of the Gamilon fleet was cutoff on the wrong side of the warp gate when it was destroyed, this becomes even more important. Indeed there is almost a full year's worth of battles and stories going on closer to home while Yamato completes the Iscandar mission.
I'm asking Shultz's same question: why didn't Earth just surrender? 'Till Yurisha's arrival, Earth had no way to stop the Gamilas fleet, the planetary bombs and the Hostile Terraforming, and it had been that way for years...
There is a general called Kotetsu Serizawa responsible for this.
Serizawa is a general, and doesn't seem to have any political power (there is no apparent military government, and there is at least Heikuro Todo above him anyway). He managed to screw the first contact up because the UN sent military ships under his command (and this makes me wonder why he wasn't hanged for that), but surrender is a political decision, one for either the General Assembly (that we don't know if it's still around) or the Security Council of the United Nations (that we did see. France was apparently replaced by the European Union, but the Security Council still exists).
Unless he's fanning the "They will not let us surrender!" flames like crazy. There seems to be no active communication between Earth and Gamilas, and Serizawa may figure that bad things will happen to him if Earth surrenders (likely extraditing him?) and thus decides he (and by extension Earth) rather go down fighting or find another solution. Wouldn't be the first "And after me the flood!" Type of Authority figure in fiction after all.
The thing is, how can he do it? He doesn't have that power over either the Security Council or the military... Unless the Gamilans asked for surrender only once before starting bombing, he couldn't have done anything.
Considering the reveal that the Earth fleet actually fired at the Gamilons first, Gamilas probably would not have accepted any sort of human surrender anyways, considering how ruthlessly they put down planetary rebellions. The high ranking Earth officials who ordered the attack probably realized this as well and decided standing and fighting was their only chance at survival.