By Peter Bergen, CNN National Security Analyst

(CNN) -- President Trump is picking on the wrong guy if he thinks the revocation of John Brennan's security clearances is going to intimidate or silence him. The man who is in many ways the architect of the war on militant jihadists is not going to be easily bullied.

Former CIA director Brennan is not just any critic of Trump: unlike many others, he doesn't come from the left. In fact, Brennan is the engineer of some of the most aggressive American efforts to eliminate jihadist terrorists.

In person, Brennan, who grew up in a devout Catholic working class family in New Jersey, is serious, even stern, not big on small talk and intolerant of BS.

President Barack Obama trusted Brennan deeply on counterterrorism issues and Brennan played an important role in the decision to carry out the operation that killed Osama bin Laden in Abbottabad, Pakistan, in 2011.

Key Obama Cabinet officials, such as Secretary of Defense Robert Gates and Vice President Joe Biden, advocated against authorizing a US Navy SEAL raid in Pakistan because of all the risks involved in such an operation, which were compounded by only circumstantial evidence that bin Laden was living in Abbottabad.

By contrast, Brennan urged a go on the raid. He told Obama that the CIA officials who had developed the intelligence on Abbottabad were, as he recalled in an interview with me later, "the people that have been following bin Laden for 15 years. This has been their life's work, this has been their life's journey, and they feel it very much in their gut that bin Laden is at that compound. I feel pretty good, if not certain, that bin Laden is at that compound."

On the morning of April 29, 2011 at the White House Brennan again strongly recommended the SEAL operation, just before Obama gave the final order to authorize the raid.

A fluent Arabic speaker who was CIA station chief in Saudi Arabia before 9/11, Brennan was tapped in 2003 by George W. Bush to run the Terrorist Threat Integration Center (TTIC), which was the first post-9/11 effort to "connect the dots" of all American intelligence flows. TTIC was set up to avoid what happened on 9/11 when information about two of the hijackers that was known to the CIA was not shared with the FBI in a timely fashion.

This improved intelligence-sharing was a key recommendation of the 9/11 Commission.

In January 2009, Obama made Brennan his homeland security and counterterrorism adviser.

From a windowless office with low ceilings in the basement of the West Wing of the White House, Brennan oversaw a vast expansion of the covert US drone program, which put significant pressure on al Qaeda and its affiliates in Pakistan and Yemen.

In 2008, during President George W. Bush's final year in office, there were 36 CIA drone strikes in Pakistan. In 2010, during Obama's second year in office, there were 122 drone strikes in Pakistan, according to New America data.

During Bush's two terms, there was only one CIA drone strike in Yemen, while in 2012, there were 56, according to the New America data.

Obama subsequently made Brennan director of the CIA in 2013, and he served for four years. Today, Brennan is back at Fordham as a senior fellow where he once studied as an undergraduate. (I am also a fellow at Fordham's Center on National Security.)

Brennan is already firing back at Trump in the New York Times, writing, "Mr. Trump's claims of no collusion [with the Russians] are, in a word, hogwash." This is a serious charge coming from a former director of the CIA.

Trump just picked on the wrong guy.