Swat 3. Don't let others agitate and don't argue with them. I'm asuming Remagen has a very bad economical/infrastructure situation including military. Plus, they built off scraps of Syriak so...
The Slavic Union as the head of the alliance, informs the rest of the countries not to get involved in fighting,provoking or questioning Rossiya. They spread word in the alliance that this can be used as a proper casus belli in future if needed.
DAV invites the new democratic country into the alliance.