What to Know About ISIS Leader Abu Bakr al-Baghdadi As U.S.-backed Iraqi and Kurdish forces near Mosul, his location is in question.

 -- U.S.-backed Iraqi and Kurdish forces press forward in their efforts to release Mosul, the second largest city in Iraq, from its two-year long occupation by ISIS.

At the same time, U.S. officials have indicated that a second front against the terror group’s administrative capital in Syria -- Raqqa -- could begin within weeks.

As these ISIS strongholds come under assault, the whereabouts of the extremist group’s leader, Abu Bakr al-Baghdadi are in question. According to Col. John Dorrian, spokesman for Operation Inherent Resolve, "If we knew where he was, he would be killed at once."

While al-Baghdadi’s exact location may not be known, some U.S. military analysts suspect he is holed up in Mosul. Officials say he has spent more time in Mosul than in Raqqa over the past two years, and there is no evidence he is in Syria at this time.

Here’s some of what is known about the secretive leader.

WHO IS ABU BAKR AL-BAGHDADI?

On June 29th, 2014, the jihadist extremist group ISIS declared the formation of a caliphate, an Islamic state, encompassing territory the organization seized in a lightning-fast run of terror across Iraq and Syria. Naming himself Caliph, or leader of the declared state, was Abu Bakr al-Baghdadi, an Iraqi born in Sumara in 1971.

Days later, in early July, a man purported to be al-Baghdadi appeared during Friday prayers at a mosque in Mosul, the city considered the biggest prize in ISIS’s march across the region. The appearance occurred during Ramadan, the holiest month in the Islamic year.

At that time, al-Baghdadi confirmed the creation of the Islamic state and called on his followers to "obey me as far as I obey God."

Since then, the ISIS leader has not been seen in public and only rarely heard from.

"We really don’t know that much, certainly not as much as we would like to know about his background, and especially about his location," Former National Counterterrorism Center director and former ABC News consultant, Matt Olson, said. "He’s extremely secretive and he’s proven to be very elusive in terms of intelligence gathering efforts by the U.S. and others."

An alleged audio speech by al-Baghdadi was released just a few days ago. It was the first time an audio message purported to be from the ISIS leader has appeared in ten months.

According to an English translation by the SITE Intelligence Group, al-Baghdadi renewed efforts to motivate his fellow Sunni Muslims by claiming enemy Shi’a Muslims will destroy them, urging them to "start your actions" in Turkey and Saudi Arabia.

While the military would not confirm the authenticity of the tape, "It is quite clearly an effort on the part of Daesh to communicate to their fighters," Col. Dorrian said. Daesh is an alternative name for ISIS.

A NOM DE GUERRE

Abu Bakr al-Baghdadi is the nom de guerre –- or battlefield alias -- of Ibrahim Awwad Ibrahim al-Badri. He was already known to U.S. and Iraqi officials when he named himself as the Caliph in 2014.

During the Iraq war, al-Baghdadi was held for ten months at American-run detention centers in Iraq, including Abu Ghraib and Camp Bucca.

An Islamic scholar, al-Baghdadi was a member of al-Qaeda in Iraq, prior to the group severing ties with the broader Al-Qaeda network. Officials believe he was responsible for several large scale attacks in Iraq after Osama Bin Laden’s death at the hands of U.S. special operation forces in May, 2011.

"He’s got a long background in being a militant. He sort of started down this path as early as 2003," according to Olsen. "He’s been in military circles and learning militant trade craft for in excess of a decade."

IS AL-BAGHDADI IN COMMAND?

As ISIS fighters dig in to defend their territory in Mosul and other areas, is al-Baghdadi in charge of the fight?

Referring the latest purported audio message from al-Baghdadi, Col. Dorrian said, "One of the interesting things we’ve seen in this English translation of this is that Baghdadi is saying, 'Don’t fight amongst yourselves.' This is the type of thing that a leader who’s losing command and control and ability to keep everybody on the same page says."

Some U.S. military commanders have said there are signs that he and a central leadership are guiding the fight. "What we saw in the Manbij fight was direction from Baghdadi to his fighters to fight to the death," Gen. Joseph Votel, Commander of U.S. Central Command said in an October briefing.

"So, I do think there is direction coming from the centralized leadership," he said. "But again, we have to respect our enemy and we have to recognize that he has leadership at the lower level that is also going to continue to make decisions."

Secretary of Defense Ash Carter announced in late October that 35 ISIS commanders in Mosul, some at the highest levels of leadership, had been killed in the three months leading up to the offensive to retake the town.

"In fact, you might say the most dangerous job in Iraq right now is to be the military emir of Mosul," Carter said while in Paris to meet with Coalition partners.

"We found that they had enough leadership experience and militant experience in their ranks that they could delegate a fair amount of authority to mid-level leaders," counterterrorism expert Olsen said. "For operational purposes they didn’t have to rely on Baghdadi or anyone in Raqqa giving direction."

The U.S.-led coalition formed in September of 2014, just months after al-Baghdadi declared the formation of the caliphate. With the United States leading, 67 countries and other partners have worked to push ISIS fighters back on the battlefield, retake territory the group seized in Iraq and Syria and prevent its expansion to other parts of the globe.

Nearly 16,000 airstrikes against ISIS targets in Iraq and Syria have been conducted by the U.S. and a small group of other coalition members.

With nearly 6,000 American advisors -- service members on the ground to advise and assist, but not engage in combat -- Iraq security forces have been able to retake more than 50 percent of the territory ISIS held, including cities like Ramadi and Fallujah. The Iraqis are now concentrating on Mosul.

In Syria, the United States has inserted 300 special operations forces to work with the opposition, Syrian Democratic Forces.

In an Orlando speech following the Pulse nightclub attack, President Obama said that 120 top ISIS leaders had been killed up to that point.

"ISIL is under more pressure than ever before," he said. "ISIL continues to lose key leaders." Among them are military commanders from Mosul, Fallujah and a leader who planned attacks overseas.

"Our message is clear," the President said. "If you target America and our allies you will not be safe. You will never be safe." U.S. officials have said they are getting closer to honing in on al-Baghdadi, as well.

"We are getting closer and closer and closer to the very core," McGurk said, "It’s really a matter of time for him."

A $10 MILLION REWARD

The United States government’s Rewards for Justice program offers up to a $10 million reward for information leading to the arrest of al-Baghdadi.

Only the leader of al-Qaeda, Ayman al-Zawahiri, who is higher up on the State Department’s Most Wanted list for terrorism, has a higher reward amount: up to $25 million.