When you buy Infantry, and use it to trade, and build up, and push forward… then you also preserve your initial ARM, ART, FIGs, and BOM.
Those initial 10 ARM and 6 FIGs of Germany can do a heck of a lot of damage, without ever being at risk themselves, if Germany buys oodles of INF.
In fact, every nation has plenty of “punch” at the start. What they all lack is MASS. And mass is most economically provided by INF.
The nation that trades with INF, backed up by a few FIGs, is in FAR better shape than the nation that trades with INF and ART or ARM. The nation that does not have to trade, but instead takes and HOLDS because of massive INF stacks is even stronger.
4 TRNs, whether loaded with INF only, or with INF/ARM combos are equally as useless against 20 INF. The attacker DIES, period. A BIG stack of Infantry, backed up by a few ARM or FIGs is a hell of a lot more deadly than the same IPC value of FIGs and ARM alone.
And finally… the dice element… the more dice you roll, the greater the odds of a hit, even of low grade potential hits. So pile on the 1’s. If they hit, BONUS! If they miss, your attack power is almost unchanged for the next round. And if you preserved those starting high value units, and maybe added a few more here and there, well then you can be assured of doing a heck of a lot of damage, and being able to do some literally KILLER strafes.