How it works
- Russia declares war on Bulgaria
- On the surprise impulse, it invades with an INF division for free. No matter where the Bulgarian unit is placed, it will not be able to cover the entire Bulgarian coast. Usually the unit is ground-struck with Russia's generous # of bombers.
- On the follow-up impulse, land with a big HQ like Zhukov and start moving to capture the entire country.
Why it's an exploit
What makes this tactic effective is the economic damage it inflicts on the Germans. Specifically, because of Russian aggression, Russia ships one less resource to Germany because they "aligned" them. This is clearly counter to the spirit of the rules since the intention is that Germany gives up resources for German aggression— not the other way round! Another clue that this rule is an exploit is that it relies on a specific optional rule to work: namely, SCS invasion and transport.
In addition, when Russia cuts the rail line— which is almost impossible to stop, the Russians will cut off the Turkish resource (or the Germans will be forced to ship it using Italian convoys). It's also fairly easy for Russia to capture the Bulgarian resource and start shipping it for themselves. All this adds up to an almost 3 resource swing for very little risk to the Russians.
Historically, it makes little sense since Bulgaria was considered to be in Germany's sphere of influence under the Molotov-Ribbentrop pact and was nominally friendly towards the Russians as well. The idea that the Russians would launch a brilliant amphibious invasion of a friendly nation (and then be rewarded for it!) is preposterous.
How can it be fixed?
Probably the easiest way to fix it is to add Bulgaria to the list of countries that allow Germany to break the pact (with the exception that Russia may enter Bulgaria if Russia is allowed to align Bulgaria).
The cost for this can be high - it's a (9) for USE so it's worth quite a lot of build points to the allies as well as the Axis.
Also, a German player with a MTN corps and an ATR can make it very risky for the Russians to take the capital.
I do think that the USSR attacking Bulgaria and having Germany align it (or any other Axis power) shouldn't reduce a pact chit though.
By current RAW when the Soviets DOW on Bulgaria they gain 2 resources, the one in Bulgaria and the one less pact resource they send to Germany when Germany aligns it. Germany loses the pact resource and can no longer rail the Turkish resource. Italy must be active and willing to risk a CP in order to try and transport that resource. On top of this 3 or 4 resource swing the Bulgarian force pool is gone, 13 BPs, and the Bulgarian resource can not be recaptured till some time after the start of Barb.
Please see our groups only house rule in the No Bess section of this website. Basically this makes Bulgaria less attractive and in trade the No Bess Gambit is removed. Personally with current RAW I regard the Soviets taking Bulgaria as being exceedingly attractive. In fact if one checks the FAQ one will see confirmed by Harry that one may demand Bessarabia, see if Germany allows or forces a DOW, and then DOW on Bulgaria the same impulse. So if one is set for a DOW on Romania it makes perfect sense to go ahead and do Bulgaria.