I found a very interesting piece of information on my PC. I played once as Romania, and guaranteed the independence of Poland. When Nazi Germany DoWed Poland on 1 September 1939 Romania was automatically drawn into war together with the Allies, as the Leader of the ad-hoc alliance against the aggressor. Having no chance of staving off the Axis advance, Romania made peace almost two weeks later as the alliance leader, forcing Poland and the Allies to peace with Germany. Poland was saved, but the Soviet Union did attack Poland in 1941, and Germany later.
Thus, issuing an independence guarantee is a very serious decision which could bring you at war with a third state without the Threat increase accompanying a Declaration of War. The downsides of such a path to war are plenty. First, you don't control when the war occurs, and declaring ahistorical security guarantees increases the probability of non-scripted DoWs and other events. Second, once your protégé get attacked you're automatically at war with a suddenly hostile entire alliance, usually the Aggressors being the Axis or the Comintern. Third, you must keep your army alert of war occuring anytime at your doors after 1938, which entails high economic costs and losing the advantage of knowing OTL history. At last, depending on your political leaning and alliance policy in the diplomatic arena, your long time plans for the path of your country could get an unexpected painful turn, setting you in great danger, especially if your nation is a minor power or a lower major.
Attention: Proclaiming an Independence Guarantee cannot be cancelled, unless the protected country disappears.
