[ought-six]

“The Tsars actually had more success with pan-Slavism...”

Yes; and that’s a major reason why Russia entered WWI: it’s ties with Serbia.

[pierrem15]

One of the primary causes of WWI was that the rules of the great power rivalry in the Balkans were not clear. The Russian ambassador to Belgrade effectively gave the Serb nationalist factions a blank cheque to do as they pleased, without the ambassador informing St. Petersburg. The French ambassador in St. Petersburg was doing the same with the Russians, and the British foreign secretary had promised the French a British declaration of war should war with Germany come without informing the rest of the British government.

So a handful of diplomats set the stage for the conflagration without their own governments fully understanding what was going on.

Our own failure to reconcile our rhetoric (NATO open to all post-Soviet states) with the reality of our commitment is also a similar ambiguity here. The Germans are also to blame for following their own narrow self-interest at the expense of their EU and NATO allies in Eastern Europe (especially Poland), as well as the US and Ukraine. The SDP decided to continue its Ostpolitik with Russia despite repeated warnings that Germany's dependence on Russian gas would turn into a big problem because Putin was paying them off and German business liked the cheap gas.