The U.S. president is considering involving Moscow in nuclear negotiations with Iran, which have been bilateral until now. It is no secret that Vladimir Putin is furious about the destruction of a significant part of his air fleet after the worst attack since World War II on his bases and the new attack on the Crimean Bridge.

Ukraine may have been underestimated before its elaborate attacks on Russian bombers dented Moscow's military capabilities - but will it substantially shift the balance of the war?