WASHINGTON - US President Barack Obama, in a rare prime-time speech designed to reassure a jittery nation, vowed Sunday that America will destroy the Islamic State group and hunt down its followers at home or abroad.
Facing questions about his leadership and strategy, Obama harnessed the highest trappings of US power to calm a country put on edge by a rampage in California that killed 14 Americans.
"After so much war, many Americans are asking whether we are confronted by a cancer that has no immediate cure," said Obama in a solemn address from the Oval Office, adding that the San Bernardino massacre was evidence of an "evolving" and increasingly homegrown threat.
As a father of two daughters, Obama said, he could imagine himself or his kin in San Bernardino or Paris.
"Here's what I want you to know," he told the country. "The threat from terrorism is real, but we will overcome it. We will destroy ISIL and any other organization that tries to harm us."
"Our military will continue to hunt down terrorist plotters in any country where it is necessary." Obama urged Muslims in America and around the world to "decisively and unequivocally reject the hateful ideology that groups like ISIL and Al-Qaeda promote." He detailed a multi-pronged strategy against Islamic State that will rely as much on community action, high-tech and countering propaganda as military force.
It is just the third time Obama has delivered an Oval Office address - deployed by presidents since Harry Truman to convey resolve in the face of a national crisis.
First was when the Gulf of Mexico was being flooded with crude oil and later to mark the end of combat operations in Iraq.
A senior administration official said the speech was designed to convey the seriousness with which Obama was taking the shootings in San Bernardino, which are being investigated as a terror attack.
On Wednesday a young married Muslim couple dropped off their six-month-old daughter with her grandmother, donned tactical gear and opened fire on an office party full of his coworkers.
Obama said the pair "had gone down the dark path of radicalization, embracing a perverted interpretation of Islam that calls for war against America and the West." "They had stockpiled assault weapons, ammunition, and pipe bombs. So this was an act of terrorism."
But he added that there was "no evidence that the killers were directed by a terrorist organization overseas or that they were part of a broader conspiracy here at home."
Both shooters died in a hail of police bullets a few hours later, leaving questions about how, when and why they may have become radicalized.
Islamic State has praised the San Bernardino attackers, US-born Syed Farook and his Pakistani wife Tashfeen Malik, as "soldiers" of its self-proclaimed caliphate, while stopping short of claiming outright credit.
In an interview with Italian newspaper La Stampa, Farook's father suggested his son approved the ideas of the Islamic State group and was fixated with Israel.
Woven throughout Obama's address was a plea for unity.
"We cannot turn against one another by letting this fight be defined as a war between America and Islam," he said, facing down some of his shrillest critics who have called for a registry of Muslim-Americans.
"ISIL does not speak for Islam. They are thugs and killers. Part of a cult of death" he said, "they account for a tiny fraction of a more than a billion Muslims around the world." "If we're to succeed in defeating terrorism, we must enlist Muslim communities as some of our strongest allies rather than push them away through suspicion and hate." But he also pressed America's feuding political factions to rally together.
The latest outrage has prompted little of the patriotism-fuelled solidarity that marked the aftermath of the 9/11 attacks.
After two decades battling jihadism from Afghanistan to Boston, Americans appear increasingly divided on the nature of the problem and how to respond.
Republicans have demanded that Obama back a full-scale deployment of NATO ground forces to Syria and resume controversial interrogations at Guantanamo Bay, which the president wants to close.
Conservatives have also taken issue with Obama's refusal to use the phrase "radical Islam" which the White House says would confer on terrorists the legitimacy of a faith they have betrayed.
"Well, Obama refused to say (he just can't say it), that we are at WAR with RADICAL ISLAMIC TERRORISTS," Republican presidential frontrunner Donald Trump Tweeted after the address.
Obama, elected on an anti-war platform, showed little sign of meeting his political foes in the middle as he reiterated calls for gun control and ruled out a new ground war in Mesopotamia.
"Our success won't depend on tough talk or abandoning our values or giving into fear. That's what groups like ISIL are hoping for," he said.
"We should not be drawn once more into a long and costly ground war in Iraq and Syria. That's what groups like ISIL want." "They know they can't defeat us on the battlefield... but they also know that if we occupy foreign lands, they can maintain insurgencies for years, killing thousands of our troops and draining our resources, and using our presence to draw new recruits."