Back when there was still only one X-book, any comic that promised to showcase the original X-Men had immediate caché. But beneath the cover of Captain America #264 was the beginning of a storyline with major implications for the Defenders.
When the Secret Empire forced a group of telepaths to project false memories into the mind of Captain America, the star-spangled Avenger experienced alternate realities where world history took different turns. Hence the cover scene of Nazis rounding up mutants long after World War II.
One of the captured psychics was strong enough to resist the Secret Empire's controls, embedding enough mental messages into the illusions to help Captain America return to his senses.
In the midst of the Cold War, the leader of the secret organization then taunted Captain America by suggesting that he might support their nationalistic aims to level a psychic assault on the U.S.S.R. That didn't go over very well (#268).
- Captain America: You twisted lunatic!!! What I've worked for has been based upon understanding--not death! I present the American Dream! A dream that has precious little to do with borders, boundaries and the kind of blind hatred your ilk espouses!
Also captured by the Secret Empire, Gargoyle, Hellcat, Valkyrie, and Nighthawk joined the fight to stop the extremist organization from starting World War III. In a surprise turn of events, the story reintroduced Nighthawk's long-ago girlfriend (from Defenders #32) as one of the abducted psychics. When Nighthawk merely thought the team needed the help of Dr. Strange, she sent out a telepathic cry for help to the master of of the mystic arts.
The story moved to Defenders #106, as Dr. Strange assembled a rescue team with Daredevil, Daimon Hellstrom, and Beast (one of the original X-Men who appeared in Captain America's illusionary world, and an increasing part of the Defenders).