A sleepy coastal nation in the Horn of Africa, Djibouti was the last French colony to achieve independence. Today, nearly four decades later, the mainly Sunni nation has become a critical part of U.S. foreign policy.

With U.S. ground forces out of Yemen amid a civil war, Djibouti is a launching pad for drone attacks on al-Qaida and other extremist groups as well as a key transit point for Americans trying to get home.

Djibouti also is bracing for the potential arrival of thousands of refugees from across the Gulf of Aden. People of different nationalities are fleeing the fighting between Yemen's Iran-backed Houthi rebels and Saudi-supported government forces.

In part to thank the Djiboutian government for its support and to get a closer look at U.S. operations, Secretary of State John Kerry is traveling there Wednesday. A day after becoming the first top American diplomat to visit Somalia, he'll likewise be the first to make an appearance in tiny Djibouti, which encompasses an area the size of New Jersey and has less than 1 million people.

Kerry will get together with President Ismail Omar Guelleh and Foreign Minister Mahamoud Ali Youssouf. He'll then meet top U.S. military officials at Camp Lemmonier, which hosts thousands of U.S. troops, contractors and civilian workers as well as aerial drones that fly over Yemen and Somalia.

The Washington Post recently reported that conditions at the base have become chronically dangerous, citing cases of air-traffic controllers sleeping on the job and making frequent errors. The Obama administration is pressing authorities to improve aviation safety, said the report, which cited documents obtained under the Freedom of Information Act.

The United States appears more content with Djibouti's support for American citizens trying to get out Yemen amid continued fighting on the ground and the weight of a Saudi-led bombing campaign against the Houthis. Some 500 Americans have fled to Djibouti, with some 200 making their way from there to the United States. Others have remained in the country while they try to secure visas for family members or collect enough money for further travel expenses.

The fighting in Yemen shows no signs of abating. Rebels fired rockets and mortars into Saudi Arabia on Tuesday, killing at least two civilians and reportedly capturing five soldiers. Meanwhile, hundreds of families fled the southern Yemeni city of Aden — it's a boat ride away from Djibouti — after the Houthis advanced into their neighborhoods, firing indiscriminately as they took over surrounding, towering mountains. Saudi officials said "all options are open" as they weigh a response.

Aid agencies are undertaking contingency planning for a prolonged conflict in Yemen that could prompt 30,000 people to flee to Djibouti this year, a challenge in a place that is already serving as home for more than 20,000 Somali refugees.

The United States isn't alone in realizing Djibouti's geopolitical significance at the junction between the Red Sea and the Indian Ocean, two of the world's busiest shipping routes.

Members of the U.S. Congress, in particular, have taken note of China's increased investments in airport, road, railway and port projects, demanding that the Obama administration raise concerns with Guelleh, whom they believe is becoming increasingly anti-democratic while cozying up to Beijing. Guelleh has been president for 16 years.

"Djibouti's strategic importance cannot be overstated," Rep. Duncan Hunter of California said in a letter sent to Kerry on Tuesday.

Late last month, another Republican congressman, Rep. Chris Smith of New Jersey, wrote to Defense Secretary Ash Carter asking that he ensure unfettered U.S. access to counterterrorism assets at Lemmonier.

"I am concerned with this," said Smith, who heads a House Foreign Affairs subcommittee on Africa, "because of China's unprecedented investment in Djibouti and worrisome behavior by the country's longtime leader."