Bhumibol was born in the U.S. and was an important ally for Washington in combating the spread of communism in Southeast Asia during the Cold War. He met with six sitting U.S. presidents, starting with Dwight Eisenhower in 1960 and ending with President Barack Obama in 2012.
Bhumibol's passing at age 88 won't set back those ties. The U.S.-Thai relationship dates back over 180 years, and Washington wants Bangkok to remain a bridgehead for its outreach to the region. But his death comes amid uncertainty about the direction of the relationship following a 2014 military coup that prompted Washington to curb high-level government engagement.
Bhumibol had no formal political role, and he made his last overseas trip decades ago, but he was instrumental in shaping modern Thailand and its international profile. He made two state visits to the United States in the 1960s, and addressed a joint meeting of Congress.
"His Majesty the King was a close friend of the United States and a valued partner of many U.S. presidents," Obama said in a statement Thursday. "The American people and I stand with the people of Thailand as we mourn His Majesty the King's passing, and today we hold the Thai people in our thoughts and prayers."
Bhumibol was born in 1927 in Cambridge, Massachusetts, at a hospital affiliated with Harvard Medical School, where his father, Prince Mahidol of Songkhla, studied. A square in Cambridge is named for Bhumibol. Secretary of State John Kerry said that would be an "enduring memorial to the special bond he created between our peoples.