Russia can send troops into China in order to disrupt Japan.
Even Cow do not declear war on allies r1 with Japan if Russia support China.
I do not claim this is optimal play, but against a weak or unlucky German r1 (or mabye against a strong Japan player) its a good move.

Here is how you do it:

R1 Buy:

• Buy 1-3mec, the rest inf and art
• DOW Japan
• Send starting mec and tnk to Sikang and Kazakhstan
• Fly planes to Suiyuyan
  from there they can attack Amur, Chahar and Yunnan, or simply fly back to Moscow or Caucasus.
• Place mec in Stalingrad
  You may actually retreat far east USSR units towards Moscow… Depends on your strategy

R2 move the units to Yunnan or Shensi.
Collect your China NO r2?
Send Stalingrad mec to China

R3.
Now China may can-open for your mobile USSR troops so that they may target stacks that would normaly be safe. This creates all kinds of different headaches for Japan.

Pros:
Unbalance solid Japan player
Protect India and China
You may send the troops back to Russia, if you need to
Cons:
BEWARE: All USSR units away from the motherland is an invite to Germany rush!
Greater need for allied help in Moscow.

Yes its me
Who wants to play

Id much rather remove a german battleship and bomber than bid two subs myself. So my bid would be 2.

I find Sealion r3 is best combined with an India r3 crush.
(complicated move, but it involves buying harbour and airfield dowing r2, and should put 6art,6inf,11fgt 8tac and 2bmb into India jap r3 with the possibility of mec and tank blitzing in from Yunnan if not blocked) and a fast Egypt takeover by Italy.

Now Russia has to guard middle east as there is a vacuume of allied units there, forcing them to be much less effective against Germany. And for USA to counter India crush they have to be almost 100% investing in pacific the early rounds, which again slows them down from affecting the Kriegsmarine.

And tip, don’t ever do sealion r4, or youll see a good soviet player camping in Romania indefinitely.

You dont HAVE to buy navy round 1 to sealion. One strategy is to simply buy nothing and let UK deside how to coop with Germany having 96 in buypower r2. If they go soft on defence its a kill, if not you can buy something like 10 tank, 8mec and 2 inf and youll be just as good of as if you bought say 6inf and 3art r1.