Outgoing Defense Secretary Ash Carter, as well as top U.S. Army leaders, recommended against President Obama commuting the bulk of Chelsea Manning’s 35-year prison sentence for leaking classified documents, a senior defense official told Fox News.

The revelation comes as Obama has found himself on the defensive over the decision, with numerous security-minded lawmakers condemning the move and warning it sets a “dangerous precedent.” Obama is expected to defend the commutation at his final press conference in office Wednesday afternoon, amid speculation over whether more clemency decisions are coming.

But sources described to Fox News the vast extent of the potential damage done by Manning’s document leak.

"Ambassadors were forced to resign, [CIA] station chiefs had to be recalled, secret diplomatic cables were revealed," said one official, recalling some of the fallout.

Fox News also has learned Manning leaked 700,000 documents, not the 250,000 cited by officials on Tuesday. Defense officials told Fox News that Manning's actions accelerated the Arab Spring and might even have contributed to the rise of ISIS.

Two intelligence sources also confirmed that after certain Afghanistan reports were released in 2010, the Taliban “went on a killing spree,” taking out everyone who seemed to fit the description of individuals working with the U.S. 

If the report said “someone with short dark  hair was helping the U.S., the Taliban took out everyone with short dark hair. It was indiscriminate,” one source said.

Both emphasized it’s unclear whether U.S. intelligence assets were harmed  --  but said there is no question people died after the leaks at the hands of the Taliban, and this made recruiting sources that much harder in the future.

In his pardon application, Manning’s lawyer said otherwise: “None of the disclosed documents caused any real damage to the United States. Instead, these documents simply embarrassed our country by revealing misconduct by the Department of Defense and unethical practices by the Department of State.”

Manning was among 273 people granted clemency Tuesday by Obama.

The former Army intelligence analyst had asked Obama last November to commute her 35-year sentence for giving classified government and military documents to the WikiLeaks website. Manning, a transgender woman who was known as Bradley Manning at the time of her 2010 arrest, is more than six years into the sentence. After Obama’s decision, she is to be released from prison in May.

Republicans blasted the decision to commute Manning's sentence, with House Speaker Paul Ryan calling it "outrageous" and saying Obama had set a "dangerous precedent" that anyone guilty of compromising U.S. national security will no longer have to pay for their crimes.

Manning originally was convicted in a mixed verdict. In 2013, an Army judge found him guilty of espionage but acquitted the analyst of aiding the enemy. Army prosecutors were unable to prove treason by linking Manning to support for Al Qaeda via the document leak to WikiLeaks.

One name not on the list of pardons and commutations the White House announced Tuesday is U.S. Army Sgt. Bowe Bergdahl. The former prisoner of war is accused of endangering comrades by walking off his post in Afghanistan, and has asked Obama for a pardon.

A pardon would allow Bergdahl to avert a military trial scheduled for April. He faces charges of desertion and misbehavior before the enemy. The misbehavior charge carries a maximum penalty of life in prison.

Obama's spokesman declined to comment when asked Wednesday about Bergdahl.

"If we have news on this, then that's news that President Obama will make," Josh Earnest said.

Fox News’ Lucas Tomlinson, Jennifer Griffin and Catherine Herridge and The Associated Press contributed to this report.