When Colonel Ryszard Kuklinski briefly visited Poland from his adopted home in the United States last fall, people were surprised to see him, and gave him warm smiles and hand shakes. He felt comfortable in the country he loved, but from which he and his family had escaped in 1981, and where for two decades Poles have been arguing about his legacy: Was he a patriot? Was he a traitor? In betraying Soviet secrets and those of its allies in the Warsaw Pact, did he betray Poland, a pact member? Or did he serve it?   But while Poles have been wrestling with that question ever since Kuklinski was sentenced to death for treason in absentia in the mid-1980s, there has been no doubt among American officials about what Kuklinski did, or why. In announcing his death recently, George j, Tenet, the CIA director, said: “This passionate and courageous man helped keep the Cold War from becoming hot.”   CIA internal files, recently released, detail the clandestine operation-codenamed Gull-that began when Kuklinski first contacted the American Army in Bonn in 1972.  In Jan. 1973, only five months after his first meetings with the Americans, one CIA briefing paper described him as “the best-placed source” available to the United States government in the Soviet Bloc “in terms of collection of priority information,” One of the first highly classified Soviet documents he turned over, the briefing paper said, had offered details of a Soviet air defense system to which there had been no previous direct access. Kuklinski's access, the memo continued, afforded “excellent insight into the plans, actions and capabilities of the Soviet-led Warsaw Pact countries, including our best existing potential for early warning of Pact hostile action” against the West.   That was the key to what Kuklinski provided during his secret mission: critical details and insights about Soviet and Warsaw Pact weapons systems and strategies that enabled the West to understand each step Moscow and its allies would have to take to launch an unprovoked attack in Europe. Shortly after the Gull operation began, the chief of the CIA's Soviet Division wrote with some prescience that if Kuldinski was able to escape detection, the case could be “of historic significance.”   Kuklinski's most dramatic act may have been to alert the CIA about the readiness of Soviet troops to invade Poland in December 1980, which led then President Jimmy Carter to issue private and public warnings to Moscow. No invasion occurred. The CIA records are also filled with other vital material, which is less well known. In 1978, for example, he provided a 363-page Russian document that detailed the tactical and technical specifications of Soviet weaponry to be introduced into the Warsaw Pact through 1985. The CIA wrote to Kuklinski at the time that the thick report was “the single most important document that you have provided.” In 1981, Kuklinski provided details of Moscow's formation of a new operational strategy to develop fast-moving air and land forces that could break through front lines and penetrate far into NATO territory.   Over nine years of secret cooperation, Kuklinski made 63 clandestine exchanges with the CIA inside Pollard, roughly seven a year. By July 1981, he had turned over 40,265 pages of highly classified Soviet documentary intelligence, one memo said. It is worth remembering that each of those pages was the result of a single click of his camera, which he held in tense and trembling hands, knowing that at any moment he could be caught by surprise, and arrested.   Kuklinski has always said that he acted out of hatred for what the Soviet had done to Poland. Long before other Poles, he recognized that his country was extremely vulnerable as a member of the Warsaw Pact; he grasped that Soviet war plans were offensive, not defensive, and that if the Soviets launched un attack, the West would respond with nuclear weapons, but not on Soviet soil; most would hit Poland. Kuklinski decided that his country was en the “wrong side,” as he put it.    His honorable approach endeared him to the agents with whom he worked. He was not a trained intelligence officer, after all. When American officers first drove to meet him secretly in a Warsaw cemetery, they were surprised to find Kuklinski standing there in full Polish Army uniform, waving to get their attention. Although he was working with them, it didn't occur to him that someday he would be labeled and sentenced to death, albeit in his absence, as an American spy; he always felt that he had acted on behalf of Poland, doing whatever it took to keep the specter of war between the Warsaw Pact nations and the West at bay. “I have boundless faith in the rightness of what l am doing,” he wrote in the summer of 1981. “Nobody and nothing could possibly change my mind or lead me off the chosen path.”