Yes I did indeed just explain the mechanics.

If brits have 10 defenders, you should also move in 4 inf as fodder. So if you buy 8 tanks and 6 inf and want all of them to Karelia, you just attack EE with this Ge force together with one lonely inf from Karelia, and after one round of combat retreat all remaining units to Karelia. Now your 6 Ge inf even got a free bonus move, if they survave, and if the brits was not eleminated. If you unfortunately got 10 hits and killed all the brits, you must end your move in EE, and lose speed. So its importent to consider what is most crucial, killing all brits in EE and gain 3 IPC income, or keep up the speed to Moscow.