WASHINGTON — If Osama bin Laden was the founding force behind Al Qaeda, then Adam Gadahn was perhaps its leading American voice.
A California-born convert to Islam, Mr. Gadahn was long seen as an important Qaeda propagandist who, as a member of the terror network’s media arm, As Sahab, played instrumental roles including translator, video producer and cultural interpreter.
President Obama said on Thursday that Mr. Gadahn and another American-born Qaeda leader, Ahmed Farouq, were killed in January in separate strikes against terrorist targets in the Afghanistan-Pakistan border region, but that neither had been specifically targeted. Mr. Gadahn had been rumored killed several times before but had always popped up again.
Mr. Gadahn, who was 36, appeared in several Qaeda propaganda pieces from 2004 onward in which he threatened the United States in vitriolic tirades and urged Muslims living in America to conduct attacks. He was not an operational leader — unlike the American-born cleric Anwar al-Awlaki, who was killed in 2011 by an American drone strike in Yemen — but instead conveyed Al Qaeda’s message to English-speaking audiences around the globe.
“Because Gadahn was a spokesman and not an operational planner, his death will have little practical bearing on Al Qaeda’s terrorist operations,” said an assessment issued on Thursday by Stratfor, a geopolitical risk analysis company. “However, it is quite telling that As Sahab media has been uncharacteristically silent in 2015.”
Mr. Gadahn grew up on a 40-acre goat farm in Southern California. His family, seeking a life of austerity and isolation, had no running water in their home and produced their own electricity from solar panels. Mr. Gadahn converted to Islam at age 17 and was said to have left the United States in the late 1990s during a period of questioning his family’s religious beliefs and the American political system.
Relatives portrayed him as an earnest pacifist seeking a simpler and less materialistic life than he had found in California. His father, Philip Gadahn, a goat farmer and carpenter in rural Riverside County, said in 2004 that he had not seen his son in five years or talked to him in more than two years.
Later that fall, in his first video, Mr. Gadahn appeared wearing black sunglasses and with a headdress wrapped around his face. Identifying himself as “Azzam the American,” he announced his relationship with Al Qaeda and warned angrily that “the streets of America shall run red with blood.”
Two years later, on the fifth anniversary of the Sept. 11, 2001, attacks, Mr. Gadahn, this time unmasked, said in a video released for the occasion, “All the brothers who took part in the raids on America were dedicated, strong-willed, highly motivated individuals with a burning concern for Islam and Muslims.”
Within weeks, Mr. Gadahn, who had been on the authorities’ radar for years, was charged with treason and providing material support to terrorists. The State Department offered a reward of up to $1 million for information leading to his capture.
Over the next few years, he appeared in several videos, speaking sometimes in Arabic but more often in English. In June 2010, he mocked Mr. Obama in a new video, calling him “a devious, evasive and serpentine American president with a Muslim name.”