I always try to get 7inf and two tanks and ftr on karelia and Caucasus r1. Unless I give up karelia and threaten Japan in Asia on r1. Former is safest. But trapping Germany in a back and forth land WAR is never good for them if you are teaming up well as allies.
U.K.first move is usually to take Borneo and New guinea on uk1. Having bought three tanks and a bomber saving one ipc. I buy three tanks every round until Japan wins our gives up. A bomber a turn from U.K.and U.S.each turn will quickly turn Germany’s income into 20 less! Giving Russia time to hold on and press back even on both fronts!
If Japan doesn’t take back at least Borneo on j1 then U.K.has four more income until they do. Your fleet is gone but the extra turns gives allies time to rebuild and prepare for Torch and Market Garden,D-Day etc.
With U.S.taking Solomon’s first turn. The Japanese will have to decide between destroying the navies and taking India before it can build up. If they don’t take the bait you now have a sizable navy in Pacific and kjf might be a good option. Have U.S.alternate buys between Atlantic and Pacific. You can threaten to land units in Soviet far east or Japan in 1 or 2 turns with U.S.
Bottom line: Germany can’t defeat Russia with bombing raids from U.K.and U.S.and fighter support. Trading land with Russia will eat up the rest of their ipcs. Japan needs to rush to Moscow to save Germany but you will slow them down if you threaten the money islands. And threaten landing units in the far east.