Don't wait for rep. parts. With no salpeter, you won't build cavalry, which is the best offensive unit until tanks.
Infantry and cavs have the same attack value, but cavalry has 3 mov. points instead of one, which is huge. Even when tanks come by, I always keep a few (about 5) cavs for special missions: no more tanks in range, city 2 tiles from my rails, (probably) last defender; small city from rubber-less foe 2 tiles away from my network, and for which I don't really want to send lots of units; "defenders" for cities 2 tiles away from rails, and without tanks near. Until MA, cavalry always has some kind of (minor) role. Before tanks, they are crucial.
Attack Greece, I'd say. They can't really be that far if they are on your continent, IMHO. Just stack enough knights. If you don't want to, attack France now. Knights vs. musket fortified in city still gives you decent odds. Much better than cavs vs. infantry fortified in metro, at least.