NATO makes clear in its official explanation on its website: “NATO allies take decisions by consensus and these are recorded. There is no record of any such decision having been taken by NATO. Personal assurances, from NATO leaders, cannot replace alliance consensus and do not constitute a formal NATO agreement”. It’s funny - when we need to order NATO around, we do it. OTOH, when it serves the purpose, we use the NATO charter to explain that decisions must be made by consensus - and properly recorded. No deal made by any member(s) is valid, whether oral or written.
So, I guess, there was always a way around those promises. It was a power play - when it was desirable to re-unite Germany, no one wanted to fight with the Soviet army divisions in Eastern Germany. Over the following years, when Russia became less of a threat, expansion started.
I think, the guy who ruined the game was Mikheil Saakashvili, the hot headed president of Georgia - who, in 2008 (afaik, against NATO advice), attacked South Ossetia. The Russians drove in, kicked out the Georgians - restored S. Ossetia’s independence - and went home. BUT - the Russians realized that NATO meant business. Since then, they drew their red lines - and kept building up their military in order to defend them. |