The comments come amid reports that al-Zarqawi has been wounded.
In a pep talk to thousands of paratroopers Thursday, Rumsfeld likened al Qaeda's reportedly wounded chief in Iraq to a cornered Adolf Hitler during the final days of Nazi Germany.
"Like Hitler in his bunker, this violent extremist, failing to advance his political objectives, now appears committed to destroying everything and everyone around him," Rumsfeld said.
Iraqi ministers said Thursday they have information verifying rumors that reputed terrorist mastermind Abu Musab al-Zarqawi had been wounded. Al-Zarqawi is Iraq's most wanted militant and has claimed responsibility for the country's deadliest attacks.
Rumsfeld addressed the Army's elite 82nd Airborne Division, which has had 42 soldiers killed and 450 wounded in action in Iraq and Afghanistan since 2001. About 1,500 division soldiers are in Afghanistan, and about 400 are in Iraq.
Like the Japanese kamikaze attacks at the end of World War II, the suicide bombings by the followers of al-Zarqawi are a sign of desperation, Rumsfeld said.
"The Zarqawis and the bin Ladens, like the tyrants and fascists before them ... tried to destroy things they could never build, and they tried to kill people they could never persuade," Rumsfeld said.
Iraq's Interior Minister said on Thursday his office believes Abu Musab al-Zarqawi was wounded, but doesn't know if he is dead.
The statement by the Interior Ministry came hours after an Internet statement claimed the so-called "al Qaeda in Iraq" group had appointed a fill-in for al-Zarqawi, its purportedly wounded leader.
But a wound to the leader — or even death — might not cause such leadership mayhem for the terrorist group as some are speculating. CBS News' Aleen Sirgany reports that Army Brig. Gen. Carter Ham, a Pentagon spokesman, said: "While Zarqawi is an important character, his organization is bigger than just one guy."
Thursday's Internet statement, the authenticity of which could not be verified, was quickly denied in another Web site claim disputing Abu Hafs al-Gerni had taken over from al-Zarqawi.
Meanwhile, a host of sometimes-dueling statements posted by militants on Web sites made it clear there could be confusion within the group itself — or perhaps even a leadership struggle — over al-Zarqawi's status.
None of the statements could be independently verified, but many of them were posted on a Web site known as a clearinghouse for al-Zarqawi, thus increasing their chances of being credible.
The latest furor over al-Zarqawi began Tuesday when an Internet statement called on Muslims to, followed by competing statements on his health and whereabouts.
A second, on Thursday, signed in the name of Abu Doujanah al-Tunisi of the media committee of al Qaeda in Iraq — an unfamiliar name from past statements — said an interim leader had been appointed to stand in for al-Zarqawi because of his injury.