A sweeping new travel ban on citizens from a dozen nations was announced by the White House on Wednesday, reviving a defining effort from the first Trump administration to crack down on entries from specific countries.

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.

A sweeping travel ban issued by the Trump administration will prohibit individuals from Sudan to Myanmar from entering the United States. International aid groups and refugee resettlement organizations roundly condemned the new ban.