Combine any Cheese you can find.
Sov: Maxim, T70, Katyshua, Partysan, ML20, heavy call in
USF: 1919, Calliope
UKF: Snipers, mortars, Firefly, Artillery Cover
It's hilarious to see how people keep claiming allies is UP in 3v3+ lol.
(Assuming you are not playing with randumbs)
Just abuse the hell out of 1919 maxim sniper CalliOP and...
THE HOLY FIRERAIN OF OBLIVION - ARTILLERY COVER
Disclaimer: Allies top #1 in 16 games.
I don't know what map you're playing but let's talk early game. 1919 is 3 cp. If USF saves all their muni for those mgs, there should be few zookas around and no grenades. UKF snipers is T1 so they're limited in early game IS or vicker's presence. pair along just 1 sniper and 1 mortar... that's 760 MP? their map presence should be very very low. flamer 251 ftw.
Assuming you play with decent mates, just rush 251 with flamer or p2. they seem to have very low anti armor units and the correct play can destroy their early game. Fortify key positions you hold with 1-2 bunkers and they'll never get to firely/artillery cover/ ml20/katy.
How is Sov able to get partisans, ml20, and heavy call in? that's 3 separate doctrines... someone's on crack. Firefly has a thread for it since some people think it's UP and heavily reliant on munis for tulips which should be toned down.
As another person stated, only calliope and artillery cover needs to be looked at on your list. Same goes for suxton, panzerwerfer, base 25 howitzers, valentine, greyhound... AA flak HQ, flak emplacement, pgren bundle grenade