Gates argued that military action was indeed necessary to prevent a humanitarian disaster that could have sparked a refugee crisis and for preemptive purposes, namely to prevent Qaddafi's brutal killings from chilling democracy uprisings in neighboring Egypt and Tunisia, and the broader Middle East.
The "time and conditions were ripe for international military action," Gates said.
Qaddafi would "kill as many as he must to crush the rebellion," Mullen warned.
Gates also reiterated his promise that "as long as he's in this office" the U.S. would not send ground troops to Libya, a position he and President Obama feel strongly about.
"I cannot imagine what circumstances [Obama] would approve it," Gates said. "That is certainly the way he has expressed it to [Mullen] and myself."
CIA operatives, however, have been sent in to coordinate with opposition leaders on the ground in Libya in an attempt to protect them from Qaddafi's brutal attacks and push regime forces out of cities rebels had once controlled.
Gates spent most of his time during the hearing being grilled by Republican and Democrats alike about the administration's decision not to seek collaborative cooperation from Congress before the air strikes began, instead spending most of his time trying to secure international support for instituting a no-fly zone.
Last night in a classified briefing with lawmakers on Libya, Secretary of State Hillary Clinton said Obama and the administration would not necessarily abide by any resolutions Congress might pass constraining the President's ability to take military action or continue it in Libya. She said only that the administration would keep Congress informed through reports and consultations.
The statements enraged some administration critics who believe the White House has violated basic tenets of the 1973 War Powers Act, which require Congressional approval to engage U.S. military forces overseas combat. The last time Congress declared war was during WWII, and a long line of presidents have essentially ignored the act, arguing that it places unconstitutional shackles on the President's role as commander-in-chief.
Congress "has been left out in the cold on this one," said Rep. Walter Jones (R-NC), a longtime opponent of the conflicts in Iraq and Afghanistan. "There has been no consultation at all."
"We read about it in the newspapers and then we ask questions about it," said Rep. Betty Sutton (D-OH). "I think that's concerning to the Congress and I think it's concerning to the American people, and I believe rightly so."
Several times during the hearing Gates repeated a one-line defense of Obama's actions.
"The President's compliance with the War Powers Act has been consistent with the actions taken by all of his predecessors -- both Democrats and Republicans" since the law was passed in 1973, Gates said.
A resolution of support for the military action in Libya would be welcome, he noted.
That riled several Republicans who quickly predicted that such a resolution would likely fail in the House.
"I certainly would not be supporting it," said Rep. Michael Turner (R-OH). "This mission is unclear and its goals are unclear."
"This administration has not been honest with the American people that this [mission] is about regime change," said Rep. Mike Coffman (R-CO). "This is just the most muddled definition of an operation probably in U.S. history."
But Rep. Jim Cooper (D-TN), a centrist, responded by turning the tables on Congress. If Congress wants to start requiring Presidents to seek war power resolutions before authorizing military action, it needs to rewrite the laws and be more consistent in its requirements. The Senate, for instance, passed a resolution approving the creation of a no-fly zone in Libya before Obama launched the strikes.
"It's really easy to do all of this Monday-morning quarterbacking," he said. "We should be more than just arm-chair generals."
The testimony came the same morning NATO took full command of air strikes and operations in Libya. Despite reports that Qaddafi's military in the last several days had reversed rebel gains in the east, Gates said the regime's forces have been steadily eroded since the beginning of the strikes a week and a half ago.