This time we're talking about Syria where rebels have been trying to overthrow Bashar Assad since March 2011. The United States said last week it had confirmed the use of chemical agents, including the nerve gas sarin, to put down the rebellion, a "red line" President Obama has said would prompt U.S. action once it had been crossed.
Unlike 2001-02 when the focus was on Saddam Hussein in Iraq, there's no appetite in the White House to put boots on the ground. Hussein had used chemical weapons against minority Kurds and refused to allow U.N. watchdogs to examine his nuclear program while boasting of his arsenal of weapons of mass destruction.
At the time, the Bush administration rallied allies to action, presenting its case to the United Nations. Once in Iraq, however, no WMDs were found and President George Bush, then-Secretary of State Colin Powell and other members of the administration were branded liars. Speculation abounded Saddam had removed his stockpiles to Syria but there was little hard evidence.
Fast forward to 2010-11: The White House had changed hands and the new president had little enthusiasm for involvement in the rebellion in Libya against strongman Moammar Gadhafi, who after Saddam's downfall tried to make nice with the international community, ending his nuclear program and opening up his facilities to international inspection.
Then came the Arab Spring, when hopes for a democratic revolution across the Arab world blossomed. Gadhafi was bombing Benghazi and other rebel strongholds to try to put down a rebellion.
Obama had ruled out sending troops to support the rebels but finally agreed to provide air support, ordering a series of bombing runs in conjunction with NATO to take out the Libyan air force, then turned the lead over to NATO to enforce a no-fly zone. Arab states began arming the rebels to even the battlefield and Gadhafi eventually fell, ending more than 30 years of rule.
As the Libyan intervention unfolded, calls for action in Syria mounted but the administration was reluctant to get involved, saying the situation in Syria was much different, citing the terrain, ethnic make-up and lack of a united opposition.
At the same time, Obama ramped up rhetoric against Assad, warning him not to use chemical weapons against his own people, saying that would be a red line.
Charges of chemical weapons use surfaced in April but Obama said the allegations had to be thoroughly investigated before any action could be taken. In the meantime, efforts to unite the opposition and vet rebel groups for ties to the likes of al-Qaida were pushed. In recent weeks, Hezbollah, an apparent proxy for Iran, has been in the forefront of fighting on Assad's behalf, retaking areas rebels had seized in the course of the conflict.
Then Thursday, the announcement came: Ben Rhodes, Obama's deputy national security adviser, confirmed the red line had been crossed.
"The intelligence community estimates that 100 to 150 people have died from detected chemical weapons attacks in Syria to date; however, casualty data is likely incomplete. While the lethality of these attacks make up only a small portion of the catastrophic loss of life in Syria, which now stands at more than 90,000 deaths, the use of chemical weapons violates international norms and crosses clear red lines that have existed within the international community for decades," he said in a statement.
The Assad regime has claimed it was the rebels who had unleashed the chemical weapons but in a conference call with reporters, Rhodes said there's no evidence of that.
"I'd also note that we believe that the Assad regime maintains control of chemical weapons within Syria, and we have not seen any reliable reporting or corroborated reporting indicating that the opposition has acquired or used chemical weapons," he said.
Rhodes said the United States is providing support to the rebels -- both political and military.
"We also are going to act very deliberately so that we're making decisions based on the U.S. national interest as well as our assessment of what can make a difference on the ground in Syria," Rhodes said, declining to elaborate on exactly what aid to the rebels will entail beyond the $500 million in humanitarian assistance already committed, although he did say the aid will include "military support."
"I cannot detail for you all of the types of that support for a variety of reasons, but suffice it to say this is going to be different in both scope and scale in terms of what we are providing to the SMC [Supreme Military Council] than what we have provided before," he said.
The announcement came just days after Hezbollah-backed Assad forces reclaimed Qusair and fighting spilled over into Lebanon. Clashes along the Turkish border also have been reported.
Sen. John McCain, R-Ariz., who beat the drums for involvement in both Iraq and Libya, welcomed the administration's announcement.
"It's not a fair fight," McCain said in calling for a no-fly zone.
"Every bone in my body knows that simply providing weapons will not change the battlefield equation and we must change the battlefield equation. Otherwise, you are going to see a regional conflict, the consequences of which we will be paying for a long, long time."
Rhodes, however, said establishing a no-fly zone would be a complex undertaking with open-ended costs.
"It's far more complex to undertake the type of effort, for instance, in Syria than it was in Libya," Rhodes said.
"But furthermore, there's not even a clear guarantee that it would dramatically improve the situation on the ground where you have regime forces and irregular regime-associated forces essentially comingled with opposition forces in a civilian population."
Sen. Bob Casey, D-Pa., also pushed for more U.S. involvement.
"Assad must go, but this will not happen without decisive leadership from the United States," Casey said. "Yesterday [Wednesday] I spoke with the military leader of the Syrian opposition Gen. Salim Idris and he reported that the situation inside the country is dire. Thousands of Assad's troops and Hezbollah fighters are assembling outside Aleppo for a ground assault. If the U.S. is not prepared to provide more robust assistance then I fear that the moderate opposition forces will be defeated."
A statement issued by the Syrian state news agency SANA accused Washington of lying, of using "flagrant tricks to come up with any possible means to justify the decision of President Barack Obama to arm the Syrian opposition."
As for other foreign reaction, Russia, which has been supporting Assad, remained skeptical.
"The Americans have tried to provide us with information on the use by the [Assad] regime of chemical weapons, but I will be frank: The report does not seem convincing to us," Kremlin aide Yury Ushakov told RIA Novosti.
Alexi Pushkov, who heads Russia's parliamentary foreign affairs committee, called the U.S. assessment "a fabrication."
Both NATO and Britain backed the U.S. report. British Foreign Secretary William Hague said his government agreed with the U.S. assessment.
"The United Kingdom has presented evidence of the use of chemical weapons in Syria to the U.N. investigation, and we have been working with our allies to get more and better information about the situation on the ground. We condemn the deplorable failure of the Assad regime to cooperate with the investigative mission," he said.
In Brussels, NATO Secretary-General Anders Fogh Rasmussen welcomed the U.S. report, saying it makes the need for a full U.N. investigation even more important.