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President Obama in recent weeks has offered mixed messages about the threat from Islamic State militants in Iraq and Syria and his plan to confront it. Now, he plans to set the record straight and provide greater clarity about his strategy in a speech to the nation on Wednesday.

Details are tightly held, but Obama says the overarching goal is to "systematically degrade" ISIS, also known as ISIL or the Islamic State, and ultimately "defeat them," an objective that officials tell ABC News will take "years." The newly-defined policy shifts from a primarily defensive posture in Iraq - protecting American installations and personnel and avoiding humanitarian catastrophe - to a more offensive one, coming almost three years since the end of the Iraq war.

Here's what we know so far about how the policy has evolved:

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EXPANDED U.S. AIRSTRIKES: JETS AND DRONES

A broadening of ISIS targets by American warplanes and drones is already underway, with a new charge of rolling back militants' territorial gains in northern Iraq. ISIS has control over a third of the country by some estimates, with strongholds extending into Syria. U.S. airstrikes began Aug. 8 as a limited operation to protect U.S. personnel and installations in Erbil and helping avert a humanitarian disaster on Mt. Sinjar. Now they have helped to push militants from the critical Mosul and Haditha dams and beyond. U.S. forces have conducted nearly 150 airstrikes since Aug. 8.

"This is similar to the kinds of counter-terrorism campaigns that we've been engaging in consistently over the last five, six, seven years," Obama said Sunday in an interview with NBC News.

The president has signaled a counter-terrorism air campaign not unlike U.S. operations in Yemen and Somalia, where forces rely heavily on intelligence to strike key targets and eventually degrade their capacity and leadership. Obama has not yet made a decision about launching airstrikes against targets inside Syria, White House press secretary Josh Earnest said today.

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TARGETING SYRIA SAFE HAVENS

The White House acknowledges that ISIS cannot be defeated without rooting out it's strongholds inside Syria, and that doing so will involve military force. But who exactly will execute that military campaign and when it will happen remains unclear. Unlike Iraq, which has directly requested U.S. help, Syria has warned against U.S. intervention.

"We continue to develop options for countering ISIL in both Iraq and in Syria. Military options are always more effective in the context of a whole-of-government strategy and in this case, in the context of a regional coalition," Chairman of the Joint Chiefs General Martin Dempsey said during a Facebook Town Hall last week.

"In Syria, the boots on the ground have to be Syrian," Obama said Sunday. The comments suggest greater effort to arm and train the moderate Syrian opposition forces - the Free Syrian Army - that's fighting both Syrian President Bashar al-Assad and the ISIS militants.

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NO US TROOPS IN COMBAT

There are already about 1,000 U.S. troops on the group in Iraq to protect the American embassy in Baghdad, the consulate in Erbil and provide advice and assessment to Iraqi and Kurdish security forces. But Obama says there will be no American troops directly involved in ground combat. Period.

"We need to attack [ISIS] in ways that prevent them from taking over territory, that bolster the Iraqi security forces, others in the region who are prepared to take them on, without committing troops of our own," Secretary of State John Kerry explained last week. "I think that's a red line for everybody here, no boots on the ground."

The White House says an effort to train and equip Iraqi forces to fight ISIS will intensify once a new Iraqi government is formed. Several hundred U.S. personnel are working with the Iraqis at a Joint Operations Center to develop a strategy and identify targets.

Officials have not ruled out covert strikes involving U.S. special operations forces or CIA operatives on the ground.

"Is it possible that there might be some clandestine efforts that are also underway here?" Earnest said. "I'm sure that that's the case, and I'm sure that's something that, you know, I won't be in a position to talk about if they do occur."

INTERNATIONAL COALITION

President Obama has demonstrated that any military campaign will be led by the U.S. but involve a host of allies that bring different resources to the table. Who will be involved in this coalition of the willing?

The U.S. convened an anti-ISIS coalition of western powers on the sidelines of the NATO summit in Wales last week. It included: Australia, Canada, Denmark, France, Germany, Italy, Poland, Turkey and the United Kingdom.

"We are going to be as part of an international coalition, carrying out air strikes in support of work on the ground by Iraqi troops, Kurdish troops," Obama explained Sunday.

"There's going to be an economic element to this. There's going to be a political element to it. There's going to be a military element to it," Obama said.

Secretary of State John Kerry will head Tuesday to Jordan and Saudi Arabia to coordinate efforts against ISIS, the State Department announced.