Postmarks And Dead Countries

I have several covers from Vietnam postmarked Saigon 1970 and several covers from the S.S.R. prior to 1990; Lithuania and Estonia. Based on the postmarks dates, would these covers postmarked in this fashion be considered covers from dead countries?
Joel

Saigon covers should have been from the Republic of South Vietnam and would be a dead country.

Estonia & Lithuania are current those would have been issued pre-second independence during the 20th century would not be dead countries.

Actually, pre 1990 covers from Estonia and Lithuania would have USSR stamps, which is now a dead country.

Bee See, Some would look at the Soviet Union as an extention of Russia, not a dead country.

True Warrehouse, but I do not . It was an extension of Russia, but no longer is.

So they are even more interesting since it is in former territory of Russia twice.

Actually according to the reference WHERE IN THE WORLD, an Atlas for Stamp Collectors, published 1985,by Ken Wood, lists modern Estonia and Lithuania as part of the S.S.R. and not independent nations at the time of the postmark. According to Wikipedia, shows South Vietnam becoming part of the communist umbrella in 1976 apparently that the 1970 post mark was administered when Saigon was still part of S. Vietnam, no longer in existence.
Joel