These days mark a couple of significant anniversaries in United States — make that world — history.

As Russia and the United States prepare to meet in Saudi Arabia to discuss Russia’s invasion of Ukraine, there’s a notable absence: Ukraine, which was purposely sidelined from negotiations. History shows that’s a really bad idea, which contributed to losses in Vietnam and Afghanistan.

As President Donald Trump looks to expand the world’s real estate that’s under control, my students in a political science class and I wondered about U.S. Presidents and their legacy, in a discussion of hypothesis tests. We look at the presidents who added territory during their tenure, and compared them to a random sample, as well as those presidents who gave some territories their freedom, independence, or a return to another country.