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In a prime-time speech Wednesday at 9 p.m. ET, U.S. President Barack Obama intends to outline for Americans the threat posed by ISIS and his strategy for "degrading and ultimately destroying" the group, according to the White House.

Obama has been under mounting pressure to lay out a plan, particularly after he said late last month that he didn't have a strategy "yet" and that he was still figuring out exactly how to "get the job done.”

The president has said that the purpose of his speech is to tell Americans about the ISIS threat and to shore up confidence that the U.S. is capable of handling it.

Here are five things Obama is expected to cover off in his address to the U.S. public.

1. Airstrikes in Syria

The U.S. began airstrikes against ISIS targets in Iraq in early August and hasn't let up since — more than 130 as of yesterday. It was a significant move for the U.S. to involve its military in the country once again after years of war there and thousands of soldiers killed, but Obama said it was necessary to protect American lives and interests.

But ISIS militants flow freely across the Iraq-Syria border and Syria is where the Sunni jihadist group is based, so the question was raised: if the U.S. really wants to hit ISIS where it hurts, doesn't it have to go into Syria? President Bashar al-Assad is still nominally in charge in Syria, however, and he's not inviting the U.S. in the way the Iraqi government did next door.

The other problem is that striking ISIS in Syria, with or without Assad's permission, might benefit the Syrian leader, whom the U.S. wants out of power. Obama has vowed to go after extremists who try and hurt Americans "wherever they are," so tonight he will have to answer whether that means Syria. If it does, he has to explain how to go about it.

2. Boots on the ground

Obama has repeatedly said he won't put American soldiers back on the ground in Iraq to defeat ISIS. But he has already ordered troops back to Iraq to provide security at the U.S. Embassy and other facilities and to act as advisers to the Iraqi military and Kurdish forces in the north.

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In this Sept. 6 image released by NBC, Chuck Todd speaks with Obama prior to an interview for Meet the Press at the White House. (NBC/Associated Press)

"This is not going to be an announcement about U.S. ground troops," Obama said about his Wednesday speech in an interview on Meet the Press on Sunday. "What this is, is similar to the kinds of counterterrorism campaigns that we've been engaging in consistently over the last five, six, seven years." 

If Obama wants the American public to clearly understand his strategy he will have to lay out not only who is not going to Iraq or Syria, or wherever else, but who is and in what roles. Obama will likely make it clear that the U.S. intends to use its air power against ISIS, but when it comes to boots, they should be worn by Syrians, Iraqis and Kurds, not Americans.

3. Permission from Congress

Members of the House of Representatives and the Senate returned from their summer breaks on Monday and are busy answering questions from Capitol Hill reporters about whether Obama needs to get their permission to launch airstrikes in Syria or whatever else his plan may include.

Views are divided, but many say they believe the president has the authorization to act alone. He thinks so too, but he also said in his interview on Meet the Press that it's important for Congress to understand the plan and have "buy-in." Obama could signal in his speech tonight if that means holding a vote of some kind. He will have to explain what "buy-in" means.

Last year at this time he was prepared to conduct airstrikes in Syria — against Assad, not ISIS — but he sought Congress's approval and didn't get it. If the White House stops short of wanting authorization this time, Obama will likely tell Americans how he is working with Congress and keeping them in the loop. Top House and Senate leaders, for example, were invited to the White House Tuesday for a meeting, and briefings and consultations are continuing, according to officials.

4. U.S. won't act alone

Americans are war-weary, and while polls suggest public support for airstrikes in Iraq and Syria, they don't want to be dragged into another long conflict. Obama knows this and he's been indicating that the U.S. does not intend to shoulder this fight against ISIS alone.

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Obama and U.K. Prime Minister David Cameron watch a flypast on the second day of a NATO summit in Newport, Wales on Sept. 5. Britain is among the NATO partners that have agreed to be part of an ISIS plan. (Matt Dunham/Associated Press)

He needs to explain to Americans that the U.S. is trying to lead a multi-partner effort to root out ISIS that includes NATO partners and regional Arab powers such as Saudi Arabia, Jordan and Turkey. He will also need to explain that building this coalition takes time and is one reason why the U.S. hasn't yet broadened its ISIS strategy beyond the Iraq strikes.

5. ISIS threat to U.S.

Whether ISIS poses a direct threat to the U.S. homeland is a matter of debate, and Obama will need to weigh in with an assessment as he makes his case for using America's military and taxpayer dollars to tackle the group. White House spokesman Josh Earnest said Tuesday that U.S. intelligence agencies are not aware of any specific plot by ISIS to attack on U.S. soil. But that doesn't mean the group isn't a threat, he explained.

The threat the White House is concerned about, however, is the one posed by people with American or other Western passports who have gone to Syria and elsewhere to join ISIS. They could pose a threat if they return to the United States, Earnest said. Obama will need to make clear why ISIS warrants a response from the U.S. in the first place. Making his speech on the eve of the 13th anniversary of the Sept. 11 attacks, Obama will need to handle this part of his speech delicately to avoid causing unnecessary fear.