The Russians flying with the North Koreans has been well documented since the end of the Cold War. A couple of the guys became aces with more kills than the highest scoring USAF F-86 pilots, some claiming over 20 kills. This is according to the Russians who did not have as rigorous kill confirmation procedures as the UN forces.
As for Russians flying in Vietnam, that is a pretty doubtful prospect. I have not heard of any Russians claiming kills from Vietnam, and they love to tell stories like that. If anyone is interested on a very detailed look at air combat in Vietnam I highly recommend the book Clashes published by the Naval Institute Press. It is written by a retired USAF COL and F-4 pilot. At the very end of the book he addresses the subject of Russian pilots in VN and discounts it.
As and interesting side note, Russians flew Mig-21's out of Egypt during the War of Attrition from 1967-1970. The got their asses handed to them during one particular battle with the Israeli's. In the end what matters most is the pilot, not the plane.
As for Russians flying in Vietnam, that is a pretty doubtful prospect. I have not heard of any Russians claiming kills from Vietnam, and they love to tell stories like that. If anyone is interested on a very detailed look at air combat in Vietnam I highly recommend the book Clashes published by the Naval Institute Press. It is written by a retired USAF COL and F-4 pilot. At the very end of the book he addresses the subject of Russian pilots in VN and discounts it.
As and interesting side note, Russians flew Mig-21's out of Egypt during the War of Attrition from 1967-1970. The got their asses handed to them during one particular battle with the Israeli's. In the end what matters most is the pilot, not the plane.