A popular argument from Russian trolls is that NATO promised not to expand, and then expanded anyway, and therefore Russia has the right to invade Ukraine.
It is claimed that Gorbachev was promised this verbally in a meeting.
Since Gorbachev only had an international role until the dissolution of the Soviet Union in 1991 such a promise must have been made up until 1991.
The arguments against are:
In short, Russia accepted in writing the expansion of NATO here:
https://www.nato.int/cps/su/natohq/official_texts_25468.htm
with the critical part being:
”
respect for sovereignty, independence and territorial integrity of all states and their inherent right to choose the means to ensure their own security”
Former Warsaw Pact countries wanted to join NATO to avoid being invaded by Russia applied and the first invitation came in July 1997, that is after the Founding Act was signed.
The only deal on enlargement is the 1990
Treaty on the Final Settlement with Respect to Germany. where NATO troops are not to be based in former East Germany - until a new German government decides otherwise.
en.wikisource.org
Before signing the Founding Act, Yeltsin wanted to have a promise of no-expansion from Bill Clinton, but this was denied. This is shown in the notes taken from the meeting, available in the Clinton Library.
Washington, D.C., October 2, 2018 – President Bill Clinton saw Russian leader Boris Yeltsin as indispensable for promoting American interests following the collapse of the Soviet Union, often prompting him to take controversial steps to ensure Yeltsin’s political survival, according to top-level...
nsarchive.gwu.edu
Instead it was agreed to postpone discussions until after critical elections.
Putin and Russian Trolls are lying their teeth out, when they claim that NATO promised - no expansion.