I mentioned in my review of Hellsing Vol. 10 on Saturday that the Major's true target was Alucard all along. He had built all these forces, 1,000 vampire soldiers, werewolves, airships, a 'self-observation which possesses its own will' (that would be Warrant Officer Schroedinger), and expended all of it on one being. Some of them seemed to be in on the scheme (Schroedinger, for one), but others didn't expect the plan would result in their deaths. I imagine the low-level soldiers didn't even know who the real target was. They probably believed they were restarting World War 2, and it was, 70 years later, finally time for Operation Sea Lion, only with airships instead of amphibious landing craft.
When he thought he'd succeeded, when Alucard appeared to dissipate in the rising sun, the Major was happy. He was experiencing victory, finally, and it felt good to him. The fact that Integra and Seras would kill him in a few moments bothered him not a bit. He expected that. He killed someone important to them, of course they would kill him. It didn't matter, though. He had defeated the person he tabbed as his archenemy, that was enough.
The Major believes he died succeeding, but having read the remainder of the volume, I know he didn't. The thing that troubles me, why I'm doing this post, is I can't decide if that matters or not. He died feeling the rush of victory, but it was false. Those who survived know this (eventually, since it takes time for Alucard to return). To them, the Major failed. But that doesn't change the fact he felt victorious at the end, and it can never change that, because he's dead*. His feeling of accomplishment can never be taken away, so does that mean he did win, in a way?
There's a moment in the history of the universe where Alucard had vanished, and the Major thought he'd won. That moment will always exist, regardless of what follows. Integra was furious at the time with the Major for what he'd done. That moment will always exist, too. It had an effect, that's carried forward through time, so the Major did win, I think. Yet he didn't.
Since Schroedinger was a key part in the scheme, and he's a personification of the theoretical cat experiment he draws his name from, perhaps it being both is the point. At that time, Alucard is both alive and dead, and everywhere and nowhere. So the Major thinking he's gone is right, and that we learn later he wasn't dead was also right.
Or, on a less quantum physics level, perhaps it refers to the impermanence of gains made through war. Countries and peoples gain land, resources, or subjects through conquest, but those tend not to last. Empires fall apart, either because they people that were conquered rise up, the conquerors become complacent, or some new hungry group of would-be world rulers comes along. Look at Alsace-Lorraine. It was a French holding, until the Franco-Prussian War, when it was incorporated into a newly unified Germany. World War I ends, and the French take it back. World War 2 starts and they lose it again, only to regain it once the war ends. gains made can't be held, enemies defeated rise again.
* Perhaps in the afterlife he's aware he was wrong, but there's no evidence of it. That's not something the Hellsing universe makes any mention of as a possibility.