The just-married socialist mayor from Vermont was on what he called “a very strange honeymoon,” an official 10-day visit to the communist country, and he was enthralled with the hospitality and the lessons that could be brought home.

“Let’s take the strengths of both systems,” he said upon completing the trip. “Let’s learn from each other.”…

As he stood on Soviet soil, Sanders, then 46 years old, criticized the cost of housing and health care in the United States, while lauding the lower prices — but not the quality — of that available in the Soviet Union. Then, at a banquet attended by about 100 people, Sanders blasted the way the United States had intervened in other countries, stunning one of those who had accompanied him.

“I got really upset and walked out,” said David F. Kelley, who had helped arrange the trip and was the only Republican in Sanders’s entourage. “When you are a critic of your country, you can say anything you want on home soil. At that point, the Cold War wasn’t over, the arms race wasn’t over, and I just wasn’t comfortable with it.”