Like borobadger said: If you are struggling use the standard BO: MG>Gren>Gren>Gren for your first minutes.
Try to move you 2 of your Grens togehter with your MG in the backline.
The thrid Gren and your Pio can be used to cap other points and especially give close support for you MG if being flanked.
Most of the time USF will play like : Rifle>Rifle>Rifle>Lui/Captain
In numbers these are 4 squads + engi.
With "point&click attack" your MG can supress 2 Squads due to the wide angle (widest of all MGs in CoH2).
Afterwards your inf squads should take care of the 3 remaining USF Squads.
Remember never go wide with OST if you are new to them. They can easily manage to win a good micro, but small area early game.
If he is harrassing you with a Stuart stay more defensive and build a pak at min 7 or a PzGren with Schrecks (if you do, remember not to spend to manny ammo onto LMGs fro Grens).
A combination of Inf+Support is OSTs key to victory. Focus onto one ammo & fuel and dont get stressed if the VPs are ticking against you.
I wouldn`t recommend going two MGs against USF as the first two units. Through this you will increase the annyoing flanking potential.
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