The Union of Soviet Socialist Republics.
When written in the Russian language, which uses the cyrillic alphabet, it comes out as CCCP
Lead country of the Warsaw Pact, even though they might not have admitted it at the time.
Broke up after Gorbachev and glasnost, leaving a load of smaller republics such as the Ukraine and Estonia to go their own way, although the Russian Federation, the rump of the USSR, is still the most powerful, most influential and got the lion's share of the nukes.
The USSR had a huge military force and were likely to be the visiting side if we ever had to play the home game.
Small arms distributed by the Soviet Union such as the AK-47 (7.62x39mm), RPD (7.62x39mm), AK-74 (5.56x39mm), RPK (5.56x39mm) and AKM (7.62x39mm) have wound up in the hands of most 3rd world conventional armies, terrorist/militant groups and the Mafia. Hence the AK series of weapon systems are the main opponent to ISAF, NATO and UN forces in the middle east. The AK series of weapons have many considerable advantages, such as the fact they can be buried in the sand for 70 years and still operate, but they are also prone to inaccurate fire upwards of 400m (albeit the effective range of an AK-47 is around 600m). However the AK-74 series chambered in 5.56x39mm (they copied NATO) are much more accurate however they do have a shorter MBR (Maximum Battle Range) of 400m.
Pretty much every piece of teaching in the British Army prior to Iraq was centered on giving the Soviets a damn good spanking. Or, more as likely, wondering why the fuck you signed up as you count down the 12 minutes of expected lifetime on the frontline in Europe.
Because of this, when the British Army hit Iraq, a lot of the training had to go out the window with SOPs, TAMs, etc, being quickly re-written. At least it was flat and suited the armoured theory to a degree.
They also had one of the better national anthems of all our proposed enemies.
The common belief was that with superior firepower, they would steamroll the NATO forces before the US was able to fly / freight in sufficient reinforcements to bolster the lines. Several good research books (Claw of the Bears and Afghansty) suggest that in fact, the Soviet forces would have splintered once solid NATO resistance was met due to the member states of the Warsaw Pact not really giving a fuck for the Motherland and only toeing the line so they didn't get spanked.
Also, that and the fact that with a possible reservist uptake of 3 million men a year, the training would be dogshit.
Did you know, most Soviet soldiers didn't have maps or sleeping bags? Poor buggers, but I bet they didn't miss all the NavEx bullshit we have to do!