Asked whether Russia was ready to put its nuclear forces on alert, Putin said: “We were ready to do this.”

He said he fielded many calls from foreign leaders and told them “that this is our historical territory and Russian people live there, they were in danger, and we cannot abandon them.”

“It was a frank and open position. And that is why I think no one was in the mood to start a world war.”

Putin said in the documentary, that was filmed over eight months, that he had “no doubts” about the success of his operation to take back the peninsula that had been transferred from Russian to Ukrainian jurisdiction in 1954 by Soviet leader Nikita Khrushchev.