Time for some more rambling. I’m not sure if this is something that’s already been touched on in the fandom, but I was rewatching the The First Avenger recently and I’m pretty sure the train was set up by Hydra to be a trap for Bucky…
Let’s start by looking at the scene where Steve rescues Bucky from the Hydra munitions factory. When Schmidt sees that Captain America has infiltrated the facility, he sets the building to destruct. Zola sees what Schmidt is doing and he freaks the hell out.
Now, Zola is normally a groveling worm when it comes to Schmidt. He knows better than to stand up to him; but there’s something that tips him over the edge here–if just for a second.
We already know there are a handful of other munitions factories across Europe (which is part of the reason Schmidt can be so casual about blowing up this one). Wanting to save the weapons might be part of Zola’s reaction here, but that really isn’t reason enough for him to risk Schmidt’s anger (which can be deadly). At this point in time, there’s nothing in the factory they can’t afford to lose.
Except for Bucky.
Sergeant Barnes is the first one to show signs he might survive his stint in the isolation ward. He’s the first one to show signs that he might be responding to Zola’s attempts to create his own super soldier. That research is only located in one place, and Schmidt is about to send Zola’s breakthrough up in flames. The moment Zola realizes he can’t stop Schmidt, he makes a break for the lab to try to rescue his notes. Of course there’s no way he can carry Bucky out of there, so he has to make do with what he can get.
In a painful twist of fate, Steve does Zola a favor by saving Bucky.
Take a look at this standoff on the scaffold. Here the audience is meant to focus on Steve and Schmidt going head-to-head for the first time; but pay attention to Bucky and Zola. This is their standoff, too. Follow their line of sight. They’re not looking at Steve and/or Schmidt through most of this scene. They’re looking at each other, and you can almost see the realization on Zola’s face that his experiment might just be saved.
Don’t you dare look at Bucky like that, you asshole.
Also, can I just point out the look on Bucky’s face when he spots Zola?
If looks could kill.
Not to mention his face when he sees what Schmidt looks like under the mask. Sure, Bucky’s line asking Steve if he has “one of those” is meant to be a joke for the audience; but I think Bucky’s experience as a character is a lot different from our experience outside the fourth wall. He’s genuinely scared–for Steve, for himself. You can see the trace of tears in his eyes.
Bucky knows something awful has been done to him at the hands of Hydra, and he doesn’t know if he’s going to lose his humanity, too.
Jump ahead and Captain America and the Howling Commandos are now laying waste to anything and everything Hydra. Things are looking bad for our villains.
This is an interesting line, because the movie doesn’t exactly tell us what Zola’s mission is. Maybe we’re supposed to think his mission is to make sure the weapons are finished in time to meet Schmidt’s timeline for world domination. Or maybe it’s to kill Captain America. And maybe those things are part of his job, but as Zola himself says, “I merely develop the weapons. I cannot fire them.” His primary job is research and development, not tactical planning and defense.
Now that Hydra is up against a super soldier, it’s likely that Schmidt is anxious to get his own super soldiers into combat. The easiest and fastest way to complete that research, of course, is to retrieve Sergeant Barnes. (In theory, Zola could use Steve for experimentation if he caught him; but he would have to start the experiment from scratch. Peggy made it clear earlier in the film that it would take them years to find out the formula using Steve’s blood. Chances are good the same would apply to Zola. The work on Bucky is already underway, it’s Zola’s own handy work, and Bucky’s still weak enough to be an easy catch compared to Steve.)
I don’t think it’s a coincidence that, directly after Schmidt gives Zola the ultimatum to “finish his mission,” we cut to the Howling Commandos laying in wait for the train. They’re hoping to catch Zola, whose location has somehow been leaked, and it quickly becomes clear that the scummy doctor hasn’t been caught by surprise. In fact, everything indicates that Zola was the one laying in wait for them. He’s surveilling the entire train from a command center and issuing orders to strategically placed Hydra soldiers.
When Steve and Bucky board the car, Zola deliberately separates them.
Divide and conquer is a tried and true tactic, but look at the difference in the opponents sent after them. Steve is given a huge opponent armed to the back teeth with a Tesseract energy gun. But Bucky? Bucky faces off against one traditionally-armed guard. (EDIT: In a subsequent viewing I noticed he actually faces off against two guards, but the second one is barely seen and is removed from the equation fairly quickly.)
Why wasn’t that guard given an energy weapon too? My guess would be because Zola didn’t want his guinea pig harmed too badly. Bullet wounds can heal, but disintegration is forever.
It might also be telling that when Steve and Bucky are back in the same compartment together, Zola screams “kill him” not “kill them.” It’s up for debate who Zola meant for the guard to target; but since he was initially sent after Steve, it’s my assumption that’s who Zola meant for him to shoot.
As we all know, the plan goes horribly awry on both sides and Bucky falls to his seeming death. Zola is captured and, when Colonel Philips tells him that “the last guy you cost us was Captain Roger’s closest friend,” Zola barely acknowledges it with a creeptacular grin.
He knows. He knows whatever he did to Bucky would keep him alive. And, as it turns out, even as a captive Zola will gain the means to finish his little experiment.