Charles Haughey denied Ireland was neutral during top-level talks with his then West German counterpart Chancellor Helmut Schmidt.
The ex-Taoiseach also claimed that the Irish people understood and were willing to sign up to defence obligations as part of closer European integration.
State papers, just released under the 30-year-rule, show the premiers discussed Ireland's refusal to join the Nato military pact during a meeting in Bonn on March 31, 1981.
Mr Schmidt asked Mr Haughey if he could raise a "pertinent question" about whether the main reason for remaining outside the Atlantic alliance was because of Ireland's troubled relationship with Britain.
"Did this traditional position of neutrality give the Irish people the idea that they were not militarily threatened?" he also asked.
But Mr Haughey said he did not think the Irish public had given much thought to whether they were militarily threatened or not. "Ideologically and politically, Ireland was not neutral," he said, files from the Taoiseach's department show.
"Ireland was part of the West. If there was to be movement towards political integration in Europe involving defence obligations, Ireland would play its part in this. This is accepted by the Irish public."
Mr Haughey said it was the "Northern Ireland problem" that was bedevilling relations between Ireland and Britain.
During the meeting, Mr Schmidt had also asked whether there was much evidence of a Soviet naval presence in Irish waters. On a visit to Iceland he had been warned about Russians engaging in a lot of surveillance under the cover of fishing operations, and Soviet ships were also being encountered just half an hour outside German ports, the Chancellor said.
But Mr Haughey said there was "no particular evidence" of USSR activity off Irish waters. There had been Soviet fishing with factory ships close to and sometimes within Ireland's territorial waters but the practice seemed to have stopped since a 200-mile exclusion zone was brought in, he added.