An interesting piece that suggests that people have a more emotional response to moral issues when presented to them in their native language than in their second language.

A new study from psychologists at the University of Chicago and Pompeu Fabra University in Barcelona finds that people using a foreign language take a relatively utilitarian approach to moral dilemmas, making decisions based on assessments of what's best for the common good. That pattern holds even when the utilitarian choice would produce an emotionally difficult outcome, such as sacrificing one life so others could live.

"This discovery has important consequences for our globalized world, as many individuals make moral judgments in both native and foreign languages," says Boaz Keysar, Professor of Psychology at UChicago. "The real world implications could include an immigrant serving as a jury member in a trial, who may approach decision-making differently than a native-English speaker." Leading author Albert Costa, UPF psychologist adds that "deliberations at places like the United Nations, the European Union, large international corporations or investment firms can be better explained or made more predictable by this discovery."

The researchers propose that the foreign language elicits a reduced emotional response. That provides a psychological distance from emotional concerns when making moral decisions. Previous studies from both research groups independently found a similar effect for making economic decisions.
If we assume that, to start or maintain a war you need to raise the passion of the people, then you may want to do it in their native tongue, or the “passion’ may be replaced by logic and not have the same effect.