The most serious challenge to the nuclear deal may be that it does not at all address the human rights record of the Tehran theocracy or statements challenging the legitimacy of Israel. However, from the perspective of the Obama Administration and most U.S. allies, the nuclear deal is seen as a first step in empowering a more progressive trend with Iran.
With oil prices falling, corrupt officials see defense spending as their last opportunity to pocket government funds -- and they have no intention of sharing that windfall with foreign defense industry competitors. Putin's recently announced policy of substituting Russian goods for previously imported products will enable those senior officials to siphon off a significant portion of budgetary funds.
Putin wants to regain that same "respect" that the West held for Khrushchev, and he sees no other way but to underscore his own unpredictability. I suspect that the recent sorties by Russian strategic bombers over the Atlantic Ocean and the Baltic, North and Black seas are a manifestation of this new unpredictability.