The suspected attack crosses the “red line” of deterrent President Barack Obama drew last year. The White House is considering all options, from a naval assault to putting boots on the ground.

On Tuesday, Vice President Joe Biden made a lofty claim during a speech in Texas: “There is no doubt who is responsible for this heinous use of chemical weapons: the Syrian regime.”

We, on the other hand, are not so sure.

Offering little proof, the White House has assured Americans they have “undeniable” evidence that Syrian President Bashar al-Assad used chemical weapons. If so, we would like to see it.

A decade ago, we heard a different president offer similar claims against Iraq. They were false; the result was more than 6,500 dead U.S. service members.

In 2003, the majority of students were in elementary school. For most of us, the men and women fighting and dying were distant heros.

This time, the coffins would be filled by our peers. The dead would include our friends, classmates and siblings.

As the president deliberates on what actions to take and calls on leaders of other western nations, reports indicate four U.S. naval destroyers have repositioned near Syria and are awaiting further orders, according to the Wall Street Journal. They carry the same style of missile used in the Libya intervention in 2011.

It is not clear whether a military intervention would include boots on the ground. But since the President has not ruled it out, we can only assume it still is an option.

It is necessary to urge the president — the liberal law professor who first ran on a platform of ending open-ended wars in the Middle East — not to repeat the same mistake as his predecessor.

If the United States uses military force against Syria, it must rest on international support and concrete facts. Our generation cannot accept assumption, speculation or innuendo as reasons to die overseas.

Obama is not alone. The U.K. and France also are pushing for action and aligning their forces.

That is not enough. If Obama decides to take action, it should only be with the support and shared sacrifice of the majority of the Western world.

Although we understand the gravity of the situation in Syria, the president needs to more clearly define and support his reasons for intervention, if it indeed comes to that.

Decades after the Vietnam War ended, former Secretary of Defense Robert McNamara revised his stance.

“If we cannot persuade other nations with similar interests and similar values of the merits of the proposed use of that power, we should not proceed unilaterally except in the unlikely requirement to defend directly the continental U.S., Alaska and Hawaii,” he said in the 2003 documentary “The Fog of War.”

Similar to McNamara, the U.S. must learn from its mistakes.