Of the 12 countries from which travel is fully restricted, three are embroiled in bloody civil wars. Many of the other countries are also undergoing conflicts.

President Donald Trump’s latest travel limitations may keep fans from the 19 named nations from seeing their athletes compete in some of the globe’s most important sporting events in the next several years,

Here is a closer look at why the administration says it is instituting full bans on foreign nationals traveling to the U.S. from 12 nations.