The neighbor is possibly going to attack... why? Maybe because they want something you have, that they could seize by killing you? Such as your land? The term "lebensraum" comes to mind.

Communist ideology, likewise, exists to promote communist political policies, which have a number of major differences from capitalist (or, say, monarchist) policies when it comes to how natural resources should be exploited on industrial scales and how the products of that industry should be directed. Workers controlling the means of production, and so on.

As for falsifiability, it would be easy enough to imagine people going to war over a set of political issues (let's say, calendar reform or the right to be openly homosexual) which have no clear implications one way or another for industry. It's just, that doesn't happen. Gulf War 2? Oil. American civil war? Cotton, by way of slavery. WWII? Germany and Japan trying to bootstrap. Sub-saharan bloodbaths? Closely correlated to droughts, with a time lag as food scarcity propagates through the system. Without an underlying resource conflict, no war occurs.

There's always more to it than that, of course, because people are complicated. The first world war, for example, was a horrific morass of misplaced optimism and lost purposes, but when you look at the promises the leaders were making, it was always "no, really, we'll be able to push ahead and capture valuable territory at low cost THIS time!" and the reparations afterward were transparently a transfer of resources from the losers to the winners.