The White House is taking action against a NATO ally as it scrambles to end Turkey's attacks against Kurdish forces in northern Syria following the president's decision to withdraw U.S. troops from the region. President Trump signed an executive order imposing sanctions against the Turkish government and several Turkish officials, and is sending a delegation led by Vice President Mike Pence and new National Security Adviser Robert O'Brien to try to negotiate a ceasefire between the Kurds and Turkey.

Turkey's invasion of northern Syria highlights the complicated relationship between the U.S., Turkey, and the Kurds. It's the latest chapter in a long history of tension in the region.

The roots of Turkey's offensive against the Kurds date back nearly a century. The Kurds are a largely Muslim ethnic group native to the Middle East. They have their own language, culture and traditions.

At the end of World War I, western powers promised the Kurds an independent state, but that never happened. Instead, the Kurds are among the largest groups of people in the world without a state of their own. There are about 20 million of them spread out across a swathe of land that spans parts of Turkey, Iraq, Iran and Syria.

But statelessness hasn't kept the Kurds from being an ally of the United States. They joined U.S. forces to topple Saddam Hussein during the Iraq war and became key partners in the fight against ISIS, which set the stage for today.

For years, a Kurdish militant group calling for autonomy has launched violent attacks in Turkey. Turkey sees the Kurdish fighters in Syria as being linked with that militant group. So when President Trump pulled U.S. troops out of northern Syria, Turkey moved in, pledging to remove the Kurds and create a so-called "safe zone" stretching about 20 miles into Syrian territory. Turkey's plan is to resettle at least a million refugees displaced by the Syrian civil war and currently living in Turkey in the zone.

With U.S. troops out of the area, the Kurds are now turning to two U.S. adversaries: Syrian dictator Bashar al-Assad and his backer Russian President Vladimir Putin for protection.

"There is a divide between people who follow and know the Middle East and the president himself. An exasperated source said to me that this could be the end of the Trump presidency," CBS News foreign affairs correspondent Margaret Brennan said. "The president does not appreciate the implications of his decision to pull U.S. troops out of Syria, which will allow Turkey to continue its advance.

"For the people who do know the region, within the administration, they are arguing that the decision amounts to a demolition of U.S. power in the region that will only benefit Russia, Iran, Bashar al-Assad, and ISIS," Brennan said. "Yet the president is convinced that he is doing this country a favor by pulling out a relatively small number of troops. There is no broader strategy or policy. All of this is being retrofitted to fit the president's decision to withdraw."