War pervades the whole length of human history. There have been invasive wars, defensive wars, resource wars, revenge wars, civil wars, and maybe even just wars, but every war shares the qualities of violence and death on a larger scale than individuals are capable. In the Superpowers alternate timeline, there have long been few geopolitical borders and sovereign states. This state of affairs made war less frequent even though the individual strengths of states made conflict all the more bloody. The silver lining to such terrible violence is that the geopolitically simple circumstances of these wars makes their results definitive, with little back and forth over territory.
National policy toward international conflict varies from one country or time to another. Rome, for example, has been in periods of isolationism in the past after which it became an ardent interventionist in foreign wars. Encountering the Maya Conglomerate was one of the largest shifts in Roman foreign policy. It presented the Imperium, for the first time in centuries, with another state matching its own.