Shuffling units to create a breakthrough
To win UoC you will need to penetrate the enemy line to cut their supply.
You can create breakthroughs by repeatedly attacking an enemy unit. This is especially true when you play the Soviets, since their individual units are weaker than the Germans. But they do have a lot of them!
You will need to learn how to shuffle units behind your front line, enabling multiple attacks without blocking the hex they attack from.
Here is an example from the Don Offensives scenario.
The Soviets need to cut the German rail line in the first turn and drive to the Oskol River, cutting off the bulk of the German Army. There are two good choices for the point of the attack - the infantry division with three soviet corps with attached artillery facing it and the unit to the left of this on the railway line. We will attack the latter, cutting off one additional German unit.
The attack goes well - 1 loss for 3 suppressed. Early in the attack sequence, suppression is nearly as good as kills! This unit has used up its attack, so we move it back out the way to let another unit continue the assault. This time we pick the infantry unit on the far left with T34s attached. It is important that the unit has at leave one move left after the attack, so it can move off the hex to let another take its place. Otherwise the attack is stalled - very frustrating for your good units to be held up because they cannot reach the front!
The T-34 attached corps only inflicts one loss, so it too retreats and the Katyusha attached corps attacks next.
At last the german division retreats - and with only 2 suppressed strength point left, will be wiped out in another attack. Now we have to make a choice - the unit that enters the hex the German division just vacated will be stuck there because it is an active German ZOC from the two side divisions. So we bring in one of the rear corps, using its full movement - this leaves the closer corps to press the penetration further in my next move, and this corps has not attacked yet and can wipe out the retreating Germans.
Lastly, the soviet corps next to the breakthrough does an extended move (you can see this because the boundary of the move is shown in grey, not orange). It is not blocked by any ZOCs and can press through close to the river.
Remaining moves are used to create a solid line of units, making it hard for the Germans to cut off the spearhead. We check the odds for the Katyusha unit to attack - 2soviet:1axis loss. We decline this attack - though we are happy to use the soviet infantry in low odds attacks, we want to be able to follow-up on damaged units, and we have no spare armies left. You learn early in Unity of Command to make sure that every attack has a purpose, rather than just attacking because you can. Finally, the partisans are used to extend the breakthrough to the river, leaving most of the Germans Army out of supply next turn.