If the UK put 50,000 troops in Northern Ireland and had the half Royal Navy in the Irish Sea do you think that would be perfectly reasonable? Or do you think a large portion of the international community would be asking us what the **** we were doing?
I think if we just said, its military's exercise, everyone would have just forgot about it and never asked in first place.
Plus doesn't NATO conduct exercises with 50K+ personnel quite often? Like the Trident juncture in 2018 in Norway (Which borders Russia mind you).
Considering that NATO is supreme tech to Russia. That 50K personnel is probably equivalent to 300-400K of Russian Ivans with stick and stones.