President Trump’s approach to foreign policy deals is reviving a bygone imperial approach that may backfire, experts say.

Why is it so difficult to make borders impermeable? How do smuggling networks operate? What does the world look like from the perspective of undocumented migrants? What are the effects of new border ...

Ukraine’s government wants to restore the country’s frontier to where it was before Russia launched its first invasion more than a decade ago. The U.S. defense secretary said that was “unrealistic.” ...

World War I involved 32 nations from 1914 to 1919. It redrew the world map and reshaped many borders in Europe. The collapse of the Russian Empire created Poland, the Baltics, and Finland.