Going to go imperialist by invading a neighboring country that is no threat to them?

1. Not a country.

2. War isn't imperialism. Imperialism is an economic system, not just something you call any and all military action by any large country. Imperialism is an elevated form of capitalism in which finance-capital has evolved to become such a power that it merges with the state and uses all state powers in the pursuit of the expansion of capital abroad. Imperialism isn't one specific action, it is an entire state of being of a country. Like capitalism, but at its highest stage.