Veqryn:
I don’t think you read the scenario (which is pretty common.) The allies have one or two nations set up to perform 8 shore bombardments each (so potentially 16 shore bombardments per game round.) If you figure half of them hit, which is realistic since they hit on a 3 or a 4, then you are looking at the loss of about 8 units a round (since Germany can only build 10 units, that’s almost the entire round’s production!) That could realistically be as high as 12 or as little as 4, but 8 seems appropriate.
Now, most of us choose infantry first, so let’s assume you have a large stack of infantry and that’s your losses. 8 Hits = 24 IPC worth of units lost. 1 Destroyer = 8 IPC and negates at least one nation’s shore bombardments (since you cannot perform a shore bombardment AND attack naval units in the same turn.) If you negate one nation, you negate about half the hits. Therefore, you could expect a destroyer build to save 4 infantry. That is, an 8 IPC investment into a destroyer saves 4 infantry which is 12 IPC in value AND gives you 4 fodder pieces to defend with!
What I propose is, if you go this route, keep the Russian submarine in range of SZ 5. This could deter Germany from building the destroyer to stop England’s shore bombardments (usually England engages in this, since America goes Africa, Pacific or Russia). If they do build the destroyer, you can attack with the submarine, that is otherwise pretty useless, and some air power if you have it (I recommend you buy it!)
EM:
I’d trade the sub in for a tank any day! But we are given the submarine, so we have to figure out a way to use it!