If you want to attack only one unit, you have to pick the 'weakest'. If you want to attack more than one with separate attacks, you have to attack in weakest order with at least 1-1 odds on each. Units which fire can not move. Woods, towns, slopes and hills block line of sight and fire. Non-armored units in towns are treated as armored units.
Gullies act as sort of inverted slopes which units can also hide in sometimes.
Units in towns or woods have to be spotted by an undispersed friendly unit which is adjacent. Line of sight is determined very oddly, requiring following the hex pattern instead of using a straight edge. The typical vehicle can move 8-11 hexes per turn, while infantry move 1, but russian cavalry are included which move 3. Overruning units ignore weapon type versus target type modifiers, get a one column odds shift in their favor, and get a -2 CRT die roll modifier. It's by far the most effective way to attack.