The problem is that it won't likely be a direct invasion. Estonia has a significant Russian minority and we've seen this play book before:
Does NATO intervene when Russia starts (or really continues) courting pro-Russian politicians?
Does it intervene if that minority starts protesting?
Does it when that minority starts resisting?
Does it when Russia smuggles them arms?
Does it when little green men show up?
Does it when the rebels (now mostly little green men) advance West?
This go around the West tried sanctions and it obviously didn't work. Estonia is far more Western and fewer historic ties to Russia than Ukraine did. So it might not progress past step 1 in the playbook. Almost certain that Putin is going to try and likely will try for at least a couple decades to come.
Does NATO intervene when Russia starts (or really continues) courting pro-Russian politicians?
Does it intervene if that minority starts protesting?
Does it when that minority starts resisting?
Does it when Russia smuggles them arms?
Does it when little green men show up?
Does it when the rebels (now mostly little green men) advance West?
This go around the West tried sanctions and it obviously didn't work. Estonia is far more Western and fewer historic ties to Russia than Ukraine did. So it might not progress past step 1 in the playbook. Almost certain that Putin is going to try and likely will try for at least a couple decades to come.