Why do countries go to war? The classic answers include economic stress, military capabilities, and geopolitical competition. But researchers have also pointed to exclusionary nationalism, the belief that one’s own nation is superior to others. The new angle in this line of work is almost uncomfortable because it is so observable: language.

As exclusionary attitudes intensify, people tend to favor words from their own language over foreign ones, and in more extreme cases they even reject the “enemy’s” words outright. That is the key trace. Instead of treating ideology like a vague background condition, researchers look for a behavioral proxy that can be measured. In prewar Japan, the question becomes not just whether nationalism existed, but whether everyday linguistic choices mirrored its growth.

This matters because language is not just communication. It is a coordination tool. If a society starts to privilege domestic vocabulary and discourage foreign terms, it signals a tightening boundary around who belongs, what is acceptable, and whose framing counts as legitimate. Exclusionary nationalism is not merely a political slogan; it becomes something people practice. Over time, the default vocabulary of daily life can shift, and the “foreign” can start to feel not simply different, but suspect.

From a decision-maker’s perspective, the punchline is that ideology can become legible before it becomes irreversible. War is the final outcome, but the system rarely flips instantly from peaceful to violent. There is usually a runway of changes: rhetoric hardens, social norms narrow, institutions adopt new definitions of loyalty, and outsiders get squeezed out of public life. Language preference fits into that runway because it is low friction. People can adopt it without waiting for formal policy changes, which makes it a potentially earlier indicator than official statements.

There is also a governance implication. Boards, regulators, and leaders in risk-sensitive roles often rely on “hard” indicators: trade data, border events, sanctions, defense spending, and election outcomes. Those signals are important, but they move with a lag. Linguistic drift could offer a different kind of data point. Not as a replacement for economic and security analysis, but as an additional lens on how social permission structures are changing. When the culture starts rejecting an “enemy’s” words, the conflict logic is no longer theoretical. It is embedded in communication norms.

For context, this research sits in a broader effort across political science and related fields to connect beliefs to measurable behavior. Exclusionary nationalism is difficult to observe directly because it lives in attitudes, identities, and narratives. Language preference gives researchers something concrete: words are countable, categories can be coded, and trends can be tracked. The core idea is straightforward. As exclusionary attitudes intensify, word choices track that shift.

Second-order effects show up in how organizations respond. If a society is moving toward exclusionary nationalism, firms operating across borders can face soft friction first. Hiring and branding decisions can change as internal and public audiences demand more “domestic” framing. Customer communication may shift away from foreign terminology, even when the underlying product remains the same. Over time, that can become a compliance problem if language policy hardens or if regulators treat linguistic usage as a proxy for loyalty.

Finally, the strategic stakes extend beyond any single country or moment. If language preference can act as a trace of exclusionary nationalism, leaders in other contexts should think about what similar signals could look like in their own risk models. For executives, the lesson is not to overreact to every change in vocabulary. It is to recognize that when language starts drawing sharper lines, the social system may be preparing to exclude. And once exclusion becomes normal, escalations can accelerate.

In other words, the question “why do countries go to war?” has a new component: how societies learn to talk about insiders versus outsiders. Prewar Japan provides an example of how that boundary can show up in the words people choose, and how those choices can mirror a nationalist slide toward rejecting the “enemy’s” terms.