A top Olympian feared Irish athletes competing in the boycotted 1980 Moscow Games would stage an IRA-inspired demonstration.
Ken Ryan, chef de mission of the Ireland team, told diplomats he was also worried competitors would go on a drinking binge in the Russian capital due to stress.
Fifty-nine countries stayed away from the Games that year after the US demanded a boycott over the Soviet invasion of Afghanistan.
Taoiseach Charles Haughey was slow to declare the official Irish position but ultimately backed the White House amid fears of damage to trade links.
State papers released under the 30-year rule reveal that Mr Haughey's government felt that sanctioning Irish participation would not help world peace.
However, the Irish Olympic Committee defied the Taoiseach and sent one of its strongest ever teams with 48 athletes and medal hopes in boxing, cycling and on the track.
Mr Ryan, who marched alone at the opening ceremony without the Tricolour but carrying a white flag with the five-ring Olympic symbol, made his fears known in a meeting with an Irish Ambassador.
Detailing issues exercising him, he said he was worried about "the possibility of athletes organising an IRA-inspired demonstration in the Olympic village".
He said there were concerns that athletes would release tension after their events by going on a binge and that umpires and starters might try to put competitors on edge by giving unclear instructions.
Mr Ryan said the Olympic Committee supported the Government's stance and was going to Moscow "purely from the sporting point of view".