As the Trump administration continues to spar with a Democratic lawmaker over the President’s efforts to console a grieving military widow, some people are wondering: What was the slain soldier, Sgt. La David Johnson, doing that led to his death in the Western African country of Niger?

The specifics of the U.S. mission in Niger, and in Africa more broadly, have been largely overshadowed by the feud between President Trump, his Chief of Staff John Kelly, and Democratic congresswoman Frederica Wilson. Here’s what to know.

What happened to Sgt. La David Johnson?

Many of the details concerning the event remain unclear as the Pentagon continues to investigate the incident. But the Washington Post reports that, on Oct. 4, a group of eight to 12 U.S. soldiers were ambushed by around 50 Islamist militants while accompanying 30 to 40 Nigerien troops near the village of Tongo Tongo, just south of Niger’s border with Mali.

A thirty-minute firefight ensued, during which four Americans were killed. They included Staff Sgts. Dustin Wright, Bryan Black and Jeremiah Johnson, and Sgt. La David Johnson. Johnson’s remains were returned to the U.S. earlier this week.

The incident went relatively unnoticed until earlier this week, when Rep. Wilson told a local Florida TV station that, when trying to console Sgt. Johnson’s widow, President Trump told her over the phone that Johnson “knew what he signed up for.” Wilson, who said she overheard Trump’s call on a car speakerphone, has been at the center of a political firestorm over the conversation ever since.

Why are U.S. troops in Niger, and where is Niger?

When we think of the U.S. counterterrorism effort overseas, we tend to think of the Middle East. But there has long been a pocket of radical Islam in sub-Saharan Africa — particularly in the countries of Nigeria, Niger, Mali, Chad, and Mauritania — and that pocket continues to grow. The terror inflicted upon northeastern Nigeria by the radical Islamist group Boko Haram, for instance, has been well-documented.

As The Atlantic reports, U.S. troops have been in sub-Saharan Africa to combat terrorism for about 15 years. The region was considered a crucial chokepoint in the George W. Bush administration’s so-called “war on terror.”

U.S. troops arrived in Niger, an impoverished, largely Islamic country north of Nigeria and south of Algeria, in 2013 to assist the French military’s war on al-Qaeda there. There are currently about 800 U.S. troops in Niger, according to ABC News. The U.S. has spent about $100 million to build a drone base in the country.

Who was behind the attack on U.S. soldiers in Niger?

According to the Washington Post, the Defense Intelligence Agency has linked the attack to the Islamic State in the Greater Sahara. That’s a confederation of jihadists who pledged their allegiance to the greater Islamic State movement, or ISIS, in 2015. Terror experts report that the group earned credibility in the jihadist realm after a string of attacks in sub-Saharan Africa in the fall of 2015.

However, no group has yet claimed responsibility for the attack, the Associated Press reports.

What comes next?

The deaths of American servicemen in Niger have raised new questions about the U.S.’s role in sub-Saharan Africa. When Sen. John McCain, Chairman of the Senate Armed Services Committee, was asked by a reporter on Wednesday if President Trump was being forthright about what happened on Oct. 4, his answer was simply “no.” According to CNN, there have been calls for an investigation into the incident similar to the inquiry into the 2012 assault on a U.S. diplomatic compound in Benghazi, Libya that left four Americans dead and became a major talking point in the 2016 presidential election.

Regardless of the political fallout, the U.S. military presence in sub-Saharan Africa is likely to continue. In a letter to Congress in June, Trump wrote that U.S. forces in the Lake Chad Basin “continue to provide a wide variety of support to African partners conducting counterterrorism operations in the region” and will do so “until their support is no longer needed.”

Get our Politics Newsletter. The headlines out of Washington never seem to slow. Subscribe to The D.C. Brief to make sense of what matters most. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Contact us at letters@time.com.