Red lines, credibility, and history have collided over the last few weeks in Syria and here in the U.S.

What began as an effort to keep the Bashar al-Assad regime from conducting inhumane attacks on its own population may end — if certain members of Congress get their way — with American boots on the ground in yet another Arab country. And the only possible lesson one can draw from this is that Americans aren't very good at drawing lessons from history, even our most recent history.

This present crisis began when President Barack Obama, flush with what he thought was success in Libya, declared that any use of chemical weapons in Syria would be a "red line" that would prompt an American response. Obama has repeatedly renewed that warning, stating that the U.S. "will not tolerate the use of chemical weapons against the Syrian people," even as late as last month while speaking in Israel. That warning applied to "Assad and all who follow his orders," making it very clear that even a minimal use of WMDs by lower-level commanders would prompt American action.

If Obama was bluffing, someone in Syria has called him on it. Last week, the White House acknowledged that strong intelligence indicates that chemical weapons have been used at least once and possibly multiple times, although no one is clear on who used them. Almost immediately, Obama began backing away from his so-called "red line," stressing both the need to confirm the intelligence — which is certainly a good idea — and to determine whether the Assad government had ordered its use. So far, no one has given any indication that the rebels have chemical weapons to deploy, and Obama's previous statements on the "red line" were intended to remove the "loose cannon" defense from the Assad regime's playbook.

The sudden waffle from the White House has critics pouncing on Obama's lack of will and the damage it does to American credibility, specifically on proliferation issues. Eliot Abrams wrote over the weekend that Obama and his administration have talked about the Iranian nuclear program by using the exact same language as it has regarding the Syrian use of chemical weapons. Iranians will draw a clear lesson from an Obama retreat. "If such terms become synonyms for 'we will not act,'" Abrams warned, "the regime in Tehran will soon conclude that there is no danger of an American military attack and therefore no need to negotiate seriously."

That theme gained steam this weekend with senators from both parties. John McCain told NBC's Meet the Press that while he doesn't want American soldiers in Syria as a consequence of violating the "red line," he wants American intervention nonetheless, including arming the Syrian rebels and perhaps backing an "international force" to seize Assad's chemical weapons. Democrat Claire McCaskill went further, telling CBS' Bob Schieffer on Face the Nation that putting American boots on the ground might be in the works. "I don't think you want to ever rule it out," McCaskill answered when asked directly. "As Saxby [Chambliss] said, this thing has really deteriorated, and it's not really at a tipping point."

Apparently, no one has learned any lessons from what happened in Lebanon in the early 1980s, Afghanistan in the late 1980s, or in Libya over the last two years. In all three cases, lightweight American/Western intervention emboldened Islamist terror networks, unleashing waves of radicalization that undermined or toppled nearby nations, and made the region less safe as a result. The Lebanon intervention resulted in a Hezbollah attack that killed more than 240 Marines and convinced Ronald Reagan to retreat, emboldening Hezbollah and other Islamist terrorist groups. One could argue that the result in Afghanistan — the humiliation and eventual collapse of the Soviet Union — still made the effort worthwhile, even if it did produce Taliban control and a string of successful al Qaeda attacks against American interests, including 9/11. It also resulted in our 11-year war in Afghanistan, the longest war in American history and longer than the Soviet intervention that necessitated it.

There is no corresponding good argument from our Libyan adventure. The U.S.-initiated NATO intervention quickly escalated from a "right to protection" argument regarding the population of Benghazi to an undeclared war against Moammar Gadhafi. The quick decapitation of that regime did not result in a unified Libya with an enlightened self-government, but in a failed state controlled in some places by the type of Islamist terror networks we have been fighting for more than a decade. Those networks, freed from the oppression of Gadhafi, quickly organized into an insurgency in neighboring Mali, which only narrowly missed seizing control of the north African nation when foiled by a French military intervention.

Even larger-scale American interventions over the last generation have produced only moderate success. The government in Kabul is every bit as precarious now as it has been during our 11 years in Afghanistan, with corruption apparently endemic. Our first intervention in Iraq to rescue Kuwait forced us to remain in place for 12 years to enforce the no-fly zones that some American politicians want to see imposed over Syria. But in Iraq, that put us precisely in the same "credibility" vise that Obama's red-line comments have put is in today, as Saddam Hussein kept defying the ceasefire accords and U.N. resolutions. In some ways, that prompted the second intervention, which succeeded in producing a popular, democratic government, but only just barely, after an insurgency erupted that continues today.

An intervention of any scale in Syria would produce another Libya, or worse. At least in Libya, there were secular groups in the mix, mainly in Tripoli, even if they ended up without much power. In Syria, there are no good options. The New York Times reported over the weekend that the opposition is so dominated by Islamist militias that "nowhere in rebel-controlled Syria is there a secular fighting force to speak of."

In fact, there is a plethora of sectarian fighting forces, and they're not all on the same side, either. Hezbollah has entered the civil war on behalf of Assad, which pits the Iranian and Syrian establishments and their Shi'ite extremists against grassroots Sunni extremists. In no way is that a fight that should interest Americans; rather, we should be taking great care not to get entangled in it at all.

Obama should never have issued an ultimatum to Assad without being fully committed to the kind of long-term, heavy intervention that has the only hope of preventing another Libya. The White House has already begun floating trial balloons about its "regret" over the president's previous remarks. The loss of credibility after a climbdown may sting, but that at least will serve as a good lesson to follow Teddy Roosevelt's maxim to "speak softly and carry a big stick" rather than the opposite. Whatever embarrassment that may cause for the moment will pale in comparison to the trouble we could unleash by intervening once again to produce another victory for al Qaeda affiliates in the Middle East. America must stay out of Syria's civil war.