I believe for some time Germany's plan was to ally both China and Japan. They even wanted to negogiate peace between China and Japan after the 1937 invasion broke out. Is this possible in the game?
That is why Germans supported Chinese for some time against Japanese invasion and would have gladly seen peace there as it's hard to sell stuff when war is going on.
No they didn't. Most co-operation ended as soon as war broke out, and Hitler ordered that no new orders of arms and military equipment for China would be accepted.
Although outwardly Germany was still telling the Chinese that they would support them only weeks before Marco Polo, Hitler was probably already pissed off by the outcome of the Xi'an Incident. All meaningful support for China ended as soon as they signed the Non-Aggression Pact with the Soviets in about August 1937. Hitler had one of his famous rages when he heard.
Although Germany later offered to assist with peace negotiations it would have been on Japan's terms. By early 1938 Germany had strengthened their alliance with Japan and recognised Manchukuo. This reversed the position of Germany that the occupation of Manchuria in the Mukden Incident in 1931 had been illegal, and that control of the provinces should be returned to China.
The National Focus to choose China instead of Japan as an ally should only be available before war, and shouldn't be automatically accepted if China has the Unified Front. Hopefully, China won't have a generic Focus tree, but has some unique options of it's own to unify the country against Japan.
Tchang Kai Chek's son was even a Panzer officer during the Anchluss.
Chiang Kai-shek's son was not an officer in the Wehrmacht. His name was Chiang Ching-kuo. He went to university in Moscow, and returned to China around 1935, where he married, had six children and seemed to have entered the "family business" - working with his father in politics. Ching-kuo had various high offices in the post-war Republic of China (ie. Taiwan), and succeeded his father as Premier in 1972, then as leader of the KMT in 1975, before becoming President in 1978-88.
Perhaps you are mistaking him with someone else? There is a common pro-Nazi bit of propaganda that appears on many sites, trying to show that the Wehrmacht was multi-cultural and included Asians within its ranks. One of these was a man called Chiang Wei-kuo. He was thought to be the son of a senior KMT official and a Japanese woman, but the official hid the (at the time scandalous) relationship. The child was adopted by one of Chiang Kai-shek's two concubines, so grew-up as a small child as part of Chiang Kai-shek's extended family group until 1927, which also included Chiang's first wife.
Chiang Kai-shek dropped the two concubines and divorced his first wife in 1927, when he married Soong Mei-ling - known as Madame Chiang, she was the "first lady" of China, playing a prominent role in politics alongside her husband, and appears in many famous pictures and videos meeting Roosevelt, Stillwell, Churchill etc. She spoke excellent English and travelled to the US to rally support for Chinese.
The term "adopted son" is often used for Chiang Wei-kuo, but even this is tenuous, given that Chiang Kai-shek never married nor even officially recognised his relationship with the adoptive mother. Nevertheless, Chiang Kai-shek does appear to have continued to look out for the welfare of the boy, even after 1927. Publicly it was assumed that the concubine had given birth to Wei-kuo and that Chiang Kai-shek was therefore his father, but neither were true. Though interestingly Chiang Kai-shek never seems to have publicly stated the boy was not his son. It became public only in 1988.
Perhaps a little long explanation, but necessary given the subsequent claims that the leader of China supported Hitler's invasions in Europe by sending his son to fight in the Wehrmacht. And the importance that pro-Nazis attach to this man.
Chiang Kai-shek employed a group of military advisers, led at first by Seeckt and then by Falkenhyn, of former German officers. Note that Chiang employed them, paying them to work for him. They were not serving in the German Army at the time, nor were they there representing the German government. Another fact that pro-Nazis tend to "overlook". Plus Seeckt was in China before the Nazis seized power.
Seeckt and Falkenhyn and the men with them organised and trained new Divisions of the Chinese National Republican Army, building up 10 modern Divisions by the time of war with Japan, that were under Chiang's sole control. They used their contacts with industrialists in Germany to secure contracts for equipment and armaments for these, most distinctively they got German style uniforms and helmets, so are often referred to as the "German Divisions" as opposed to the locally recruited and controlled units of the NRA, which were not always so loyal to the central government. Most of the new officers of these Divisions were trained by the advisors in China.
But Falkenhyn was also able to secure positions for a small group of Chinese young men to travel to Germany and be trained by the Wehrmacht around 1936. There is nothing unusual in this - friendly nations often provided, and still do, officer training for foreign nationals, as part of reciprocal arrangements, when normally those foreigners would not be eligible to apply to join their army.
Wei-kou was one of these, and, given his links to Chiang, the most important. Wei-kuo became a Major at 28, a Lieutenant Colonel at 29, and a Colonel at 32 in charge of a tank battalion, and later a Major General. So he was a Colonel fighting in the Wehrmacht leading a panzer unit? Wow, they really weren't racists! About a 1,000 of the best German troops led by someone from Asia!! That's the message from pro-Nazis, who adorn Wei-kou's pictures across their websites and propaganda videos. And the same claim has been made previously in this forum by the main pro-Nazi cheer leader.
But, wait a second... Wei-kou was born in 1916. So he became a Colonel commanding a tank battalion in 1948? Something doesn't add up here!
The facts are that Wei-kou took command of a tank battalion when he was fighting for the NRA against Mao's forces in the Civil War, before fleeing with the KMT leadership to Taiwan. And all of his officer posts are with the NRA serving in China, starting in the 1940s, during the war with Japan.
In early 1938 he was only 21 or 22, when the Anschluss took place. The "panzer unit" he commanded was a single tank. He wasn't even an officer, but a "sergeant officer-candidate". In other words, someone undergoing officer training. And that training, arranged by Falkenhyn, was in a unit that happened to be deployed to Austria during the Anschluss.
The implication is given time and again that Wei-kou and the 5 or 6 other Chinese that were undergoing officer training at the time were serving in the Wehrmacht as volunteers, that they supported the Nazi regime and they took part in the war. And by using a number of pictures of the same 5-6 people in different poses and groups, the pictures seem to imply there were more of them than was the case. And the link to Chiang Kai-shek is intended to imply that Chiang supported Nazi Germany in their invasions, and was close to joining the Axis.
As mentioned above, by early 1938 official relations between Germany and China were severely strained. Germany began to insist that Falkenhyn and his colleagues should return to Germany, rather than continuing to assist Chiang in resisting the Japanese. With their families in Germany threatened that they might be regarded as traitors for fighting against Germany's ally, they reluctantly agreed to leave China in mid-1938. They had served Chiang for about a year during the war, and although most of the 10 "German Divisions" were destroyed in the Battle of Shanghai, nevertheless, the advisers were invaluable in preventing the Japanese from over-running China.
Oddly, the German government didn't seem to be too bothered that they still had Chinese in the army who were being trained on modern use of tanks and the combined arms tactics that would be used so successfully in Poland, France etc. Perhaps they misguidedly assumed China would still collapse and sue for peace with Japan, or the Chinese were protected by those in important positions who disagreed with Hitler, and still preferred the idea of China as an ally rather than Japan. Either way, the officer cadets didn't return to China until late in 1938 or early 1939 (depending on source). But certainly before the invasion of Poland. So no Chinese were present in the Wehrmacht during the war. And there is no record that Wei-kou was actually ever made an officer by the Wehrmacht. It appears that when their training was complete, rather than get a commission as a normal officer cadet would (ie. a German citizen who met the racial law requirements), they left Germany. And probably that was the original arrangement made by Falkenhyn.
The value of this training appears to be entirely one-sided with hindsight, it's almost like Germany helped spies who learned their tactics and methods and took them back to China. Given their small numbers and young age, they may not have contributed significantly to fighting the Japanese, but before returning full-time to China to serve in the NRA, Wei-kou went on a tour of the USA and gave lectures to senior US officers on German panzer tactics!
It's one of the greatest ironies of WW2 that Germany was defeated, in part, because Japan refused to join the war against the Soviet Union, while still bogged down in China in July 1941. Stalin could afford to redeploy significant numbers of Divisions from the Far East to the Battle of Moscow. And, even though his German military advisers had gone, they had been instrumental in bringing the NRA to a point where Chiang Kai-shek could take on the Japanese in 1937, and successfully defend the interior and most of the south of the country for eight years. This was a major achievement, given the previous 100 years of China very quickly succumbing to outside military intervention. After the end of WW2 and the civil war in China, Chiang Kai-shek honoured Falkenhyn for his major contribution to protecting the country from Japan.
Hitler's policy in mid-1937 to support the Japanese when war broke out, not only made no difference to the outcome of the Sino-Japanese War, but instead left a vacuum which was quickly filled by the Soviets and the Allies in providing equipment to China. Falkenhyn's role was taken later by US military advisers.
Personally, as I noted above, it's not even clear that the choice was there to be made by Germany alone, especially after Xi'an and the signing of the Anti-Comintern Pact with Japan. It takes two to tango, and though China was happy to take the equipment it was being sold by Germany, it doesn't mean that it was open to a formal military alliance/joining the Axis. To what end? Faced with the two internal problems of the Communists in Shaanxi and the Japanese in Manchuria, the idea that China would commit the NRA to a potential war with either the Allies or the Soviets is ridiculous.
To invade the Soviets in 1941 to divert units from fighting against the Germans in Barbarossa requires China to have first decisively defeated Japan. Since Japan really only got moral support from Germany, and little material and no manpower, then losing that support is going to make hardly any difference to Japan. It's almost impossible to transform the NRA from an army able to defend itself, especially in difficult terrain, into an offensive army that can defeat the Japanese on the north China plains and drive them out of Manchuria and Korea. Even then, it doesn't guarantee anything other than a long stalemate - China has no naval capability in the 1930-40s to retake Taiwan, never mind invade the Japanese home islands. And in game terms at least, you can see that Germany would need to send volunteers to China and lend lease of equipment, that at least matches what the Soviets and Allies supplied in the first few years, but which needs to significantly surpass what the US provided IRL, if China is to win the war. And Germany has to build alot of convoys to get it there 1937-39. It's going to impact German capability to fight the Allies.
Even if they can at first sustain Nat. China against Japan, the convoys will be destroyed quickly once war with the Allies starts. Germany can't afford to defend it's own supply convoys in European waters, never mind those taking equipment all the way to China, with Suez blocked and Allied fleets operating along the route out of Gibraltar, South Africa, Ceylon, Singapore and Hong Kong.
There is a real chance that Germany is just going to be wasting it's infantry equipment stockpiles by sending it to China, as there is no way Germany can also afford to send tanks, planes, trucks or artillery in significant quantities to make a real difference to the quality of the NRA. Germany will swap one useless ally in Asia for another useless ally that is probably bogged down in a long war of attrition, and with a fear of fighting Uncle Joe. If there is a United Front with the Communists in China, during war with Japan, then any attack on the Soviet Union by the NRA immediately causes the Chinese Civil War to break out again. So the NRA has also to decisively defeat the Communists before 1941.
Lastly, if you can go all ahistoric, and play the "what-if" game of China allying with Germany, then what's to prevent Japan allying with the Soviets in a Molotov-Tojo Pact that divides up China. Or even for Japan to join the Allies, as they did in WW1?