President Trump announced on Thursday that United States forces had killed Ibrahim Hassan al-Asiri, a highly skilled Qaeda bomb maker who built the explosives for several high-profile terrorist plots.
Mr. Trump’s announcement belatedly confirmed news reports from August 2018 that cited United States officials expressing confidence that Mr. Asiri, a leader of the Yemen-based branch known as Al Qaeda in the Arabian Peninsula, had likely been killed by a drone strike in the country the year before.
“This will confirm for the first time that Ibrahim al-Asiri, a senior al-Qa’ida bomb maker and terrorist coordinator, was killed two years ago in a United States counterterrorism operation in Yemen,” Mr. Trump said in the statement released by the White House. “The United States will continue to hunt down terrorists like al-Asiri until they no longer pose a threat to our great Nation.”
The statement did not explain the reason for the long delay. The United States is not always sure who exactly has been killed in counterterrorism operations conducted from a distance, including by a drone strike, and confirmation can sometimes come later through new intelligence such as intercepted conversations or interrogations.
The announcement also comes as Mr. Trump faces intense criticism from national security experts, many of them Republicans, over his failure to prevent Turkey from invading northeastern Syria to attack Syrian Kurdish fighters. Those Kurdish fighters have been the major ground ally within Syria for the campaign against the Islamic State. Many military and intelligence officials believe the Turkish action could make it easier for the Islamic State, or ISIS, to regenerate as the Kurds turn their attention toward their Turkish enemies.
“This is important, but it’s not news,” said Joshua A. Geltzer, who served as a senior director for counterterrorism on the National Security Council in the Obama administration.
“Credible reports have been indicating Asiri is dead for over a year,” Mr. Geltzer added. “So this announcement appears deliberately designed to portray Trump as tough on terrorism in a week when he’s proving the opposite — when he’s abandoning key U.S. partners in the fight against ISIS and thus directly raising the terrorist threat to Americans.”
Writing in the Washington Post soon after reports of Mr. Asiri’s death last year, the former deputy director of the Central Intelligence Agency, Michael J. Morell, said that, if confirmed, “he would be the most significant international terrorist removed from the battlefield since Osama bin Laden.”
“He was well known as a master of his craft, and was as intelligent as he was evil,” Mr. Morrell wrote. “When I left government in 2013, I considered him the most dangerous terrorist on the planet. His removal leaves the world a safer place.”
Though many of his plots failed, Mr. Asiri was among the world’s most feared terrorist operatives for much of the past decade. Technically skilled and imaginative about evading bomb-detection technology, he was long the target of an intensive manhunt by American military and intelligence officials.
It was Mr. Asiri who sewed a bomb into the underpants of Umar Farouk Abdulmutallab, who tried to detonate the device on an American airliner approaching Detroit on Christmas Day in 2009. The bomb fizzled harmlessly and Mr. Abdulmutallab was arrested and imprisoned.
Mr. Asiri also designed explosive devices disguised as printer cartridges and intended to blow up cargo planes over the United States in 2010, and another device meant to bring down a passenger plane in 2012, according to Mr. Trump’s statement.
But perhaps the most novel — and disturbing — of Mr. Asiri’s plots involved the recruitment of his own brother to become a suicide bomber in a 2014 plan to assassinate Saudi Arabia’s then-Crown Prince, Mohammed bin Nayef. The younger Mr. Asiri hid in his rectum a one-pound explosive device fashioned by his brother and which was remotely detonated during a meeting with Mr. Nayef, who survived.
“Although the assassination attempt failed, the brutality, novelty and sophistication of the plot is illustrative of the threat posed by al-Asiri,” Mr. Trump said in his statement.