WASHINGTON — President Trump doubled down on Monday on his decision to intervene in several high-profile war crimes cases, comparing his leniency for a handful of American service members with actions taken by President Barack Obama, which Mr. Trump said were far worse.

Under fire over his insistence that a Navy SEAL convicted of misconduct not be punished, Mr. Trump sought to defend actions that have roiled the Pentagon, angered senior military leadership and led to the firing of the Navy secretary. Mr. Trump said that his refusal to allow the Navy to oust Chief Petty Officer Edward Gallagher from the SEALs showed he was sticking up for “warriors,” and not traitors.

“You have a Chelsea Manning, who stole classified information and did many, many things that were not good and gets pardoned or whatever happened,” Mr. Trump told reporters at the White House.

He was referring to the former Army intelligence analyst who disclosed a trove of military and diplomatic documents to WikiLeaks. Ms. Manning spent nearly seven years in a military prison before Mr. Obama commuted her sentence; she was not pardoned.