I am unclear as to what point Marcus lost control of Khan.
Yep, me too. Either I missed something, or it was badly explained. Which part of the plan was whose? Or which parts were unplanned?
The way I read it initially was that Marcus unthawed Khan purely so he could work on his weapons/war strategies. Khan wanted his crew back, but Marcus wouldn't allow it, so Khan blew up the datacentre and attacked the captains' conference, then escaped, knowing that Marcus would retaliate by firing his torpedoes at Khan on Kronos (presumably this wouldn't kill them, if they were still alive). But that raises the question, if Khan could hide his crew in the torpdoes, why would he not just unthaw them? He must have had access, he did it in secret, but he couldn't unthaw them? Actually, doesn't he say that he didn't know if they were even alive? That doesn't make sense, then.
So, second possible scenario: Marcus planned the bombing and the attack, Khan was following his orders. He wanted an excuse to launch at attack on Kronos because he wanted to provoke a war with the Klingons in order to force Starfleet to become more military-focused. Khan wasn't denied access to his frozen crew but he did secretly put them in the torpedoes because he ultimately wanted to double-cross Marcus and take control himself. Of course, this means Khan would have to assume that Marcus would double-cross Khan by trying to kill him with torpedoes, and this also means that Marcus intentionally let himself get fired upon at the captain's conference, which seems pretty reckless to me.
Third possible scenario is somewhere inbetween: the bombing was Marcus's idea but the attack at the conference wasn't. Firing the torpedoes was a genuine act of revenge.
Or the fourth possibility, which, as the film was unfolding, I genuinely thought would happen: everything was Marcus's plan. He planned the bombing, he planned the attack, he put Khan's crew in the torpedoes as a way to secretly deliver them back to Khan without Starfleet knowing about it, with the ultimate goal of... well, that's where I don't have an answer. They could have gone with "he wanted Khan and his men to provoke the Klingons into a war", but there must be easier ways of doing that!
Did Marcus even WANT to provoke a war? He sends Kirk to bomb Kronos because he wanted the Klingons to blame Kirk for it. He purposely suggested a stealth attack so as to NOT provoke a war, even after Kirk suggested just going straight to Kronos anyway.
Quite honestly, I can't figure out either Marcus or Khan's motives in this film, beyond vaguely wanting power for themselves. It's as if there HAD to be a certain sequence of events, certain things had to happen, but they couldn't find a convincing way to make it happen, so it's just glossed over with woolly motives.
Can anyone explain this? Was I not paying attention?