In a Wikipedia discussion about the Annexation of Crimea by the Russian Federation 'User:力' says:
For the record, if you ask the Russians, they would say that Accession of Crimea to the Russian Federation is the correct name, but the Russians don't get to pick the article title here -- and English language sources prefer "annexation".
The implication of this is that the word accession has a more positive connotation than annexation does.
Question: If indeed the current Russian government did consider their acquisition (to use a more neutral term) an accession, why might that be a less negative connotation than annexation in their opinion?
To clarify, this isn't a question about politics per se, about Crimea, Russia, or any other political situation. Nor is it an attempt to actually interpret what some alleged "Russian" or "Western" opinion may or may not be. It's about the subtleties in meaning between the words annexation and accession in the context of politics.
This also begs the question: is accession even a term used in other political discussions? Could it just be that 'User:力' has some unique opinion of the subtleties of the words?
Merriam-Webster: annexation does not list accession as synonym.
Nor does it list annexation as a synonym of accession.
acquisition as part of their definition for accession:
2: something added : ACQUISITION // the museum's latest accessions
...but it doesn't discuss any subtleties.
Cambridge doesn't link the meaning of the two at all, even in a general sense, which is interesting since an answer here mentions the subtleties in the two in British English.