Image copyright AFP Image caption The US sees the threat posed by IS as a local problem that demands a local solution

In a hastily arranged address to the American people on Thursday night, President Barack Obama spoke for only eight minutes about his authorisation of combat and humanitarian operations in Iraq.

What he said about the evolving threat posed by the Islamic State (IS) - and especially what he did not say - depicts how far Washington's counterterrorism strategy has evolved over the 13 years since the 11 September attacks.

Mr Obama framed the IS challenge in strictly local terms, notwithstanding its ambition to re-establish a regional caliphate and its surprising ability to seize and hold territory in both Iraq and Syria,

The threat of terrorism may involve interconnected global networks, but they are animated by regional or even tribal problems that America cannot resolve.

'No military solution'

And they require local solutions that Washington will not, on his watch, attempt to impose.

Image copyright AP Image caption President Barack Obama says Iraq needs a less sectarian prime minister to replace Nouri al-Maliki

Mr Obama was explicit that American support will be limited to arresting IS's advance towards Irbil - protecting US military and diplomatic personnel in the region, providing humanitarian assistance to Iraq's besieged minorities, and continuing to strengthening Iraq's security capabilities.

Having extracted a war-weary nation from the middle of Iraq's civil war, a step that has significantly defined his presidency, the president will not place the US in the middle of it again.

Image copyright AP Image caption Mr Obama announced a limited military response to the threat posed by IS to the Yazidi community

In fact, Mr Obama went further, suggesting there is "no military solution to the larger crisis in Iraq."

He specifically mentioned the need to form a new government that all communities in Iraq can support.

He again encouraged Iraq's politicians to select a new prime minister to replace Nouri al-Maliki, one willing to govern in a less sectarian fashion.

Opposition to action

Curiously, the president did not mention Syria, preferring to define IS as primarily Iraq's problem, not a regional one requiring an international response.

A year ago, the president did just that in response to the use of chemical weapons in Syria, only to confront significant opposition to aggressive action, particularly within the UN and the US Congress.

This time, even though Mr Obama suggested IS's efforts to eliminate the Yazidi people could potentially constitute genocide, he simply announced the limited military response while engaging the UN and Congress.

America, he said, is coming to help. It's what we do.

Image copyright Reuters Image caption Fighting Osama Bin Laden in Afghanistan was viewed a global challenge by the Bush administration

Even as he ordered the military to undertake limited action, he did not suggest that IS yet represented a direct threat to the United States, an important shift in the US counterterrorism strategy.

On 11 September 2001, President George W Bush declared a "war against terror".

Given the broad ambitions of Osama Bin Laden and the al-Qaeda movement he led, the challenge was seen as global in scope.

Much like the Cold War, the world was bipolar - you were either with us or with the terrorists.

Reduced military role

Mr Bush advanced a strategy of pre-emption - act before threats fully materialise. Allies were useful, but the US was fully prepared to act alone.

In 2009, the Obama administration redefined and narrowed the war on terror it inherited.

Its emphasis was to disrupt, dismantle and defeat al-Qaeda, particularly those directly responsible for the 9/11 attacks. And over the past five years, Bin Laden was killed and his core movement decimated.

Image copyright AP Image caption Obama says the response to IS should be local and not require the deployment of substantial US forces

Now, with the threat more complex and diffuse, including affiliates, sympathisers and competitors across the Middle East and North Africa, Mr Obama continues to redefine his strategy and expand the national and international tools to combat political extremism, while reducing the military's role at the same time.

While IS has established a safe haven that encompasses growing segments of Syria and Iraq, the response does not require the deployment of substantial US forces. That is understood to be counterproductive.

This is Mr Obama's primary strategic takeaway from America's previous experiences in Iraq.

In the aftermath of the US invasion of Iraq in 2003, the war on terror was perceived as a war against Islam. Now Mr Obama sees the IS phenomenon as predominantly a war within Islam, which only the Islamic world can ultimately resolve.

PJ Crowley is a former US Assistant Secretary of State and now a professor of practice and fellow at The George Washington University Institute of Public Diplomacy & Global Communication.