I'm sometimes asked how, as someone who testified 42 years ago against the Vietnam War in which I had fought, I could testify in favor of action to hold the Assad regime accountable today.
The answer is, I spoke my conscience in 1971 and I'm speaking my conscience now in 2013.
Secretary Hagel and I support limited military action against Syrian regime targets not because we've forgotten the lessons and horrors of war -- but because we remember them.
Make no mistake: If another Vietnam or another Iraq were on the table in the Situation Room, I wouldn't be sitting at the witness table before Congress advocating for action.
I spent two years of my life working to stop the war in Vietnam, and made enemies and lost friends because of my decision to speak my mind.
So I don't come to my view on the use of military force anywhere without real reflection. I do so with an eye towards facts and reason.
I am informed by Vietnam, not imprisoned by it. And I am informed by Iraq, not imprisoned by it, either.
The faulty intelligence of the Iraq War was a legacy burned into all of us who present the case for action in Syria to the Congress: It has made us press with extra urgency to know that we are highly confident of what we speak now.
For me and for Chuck Hagel, who voted once before on an intelligence case that turned out not to be true -- and regretted it deeply -- we would never put any Member of Congress in that same position today, period.
I understand the temptation to remember Vietnam and Iraq and reflexively paint any subsequent possible military action with the same brush.
But to do so ignores what Syria is, and what it isn't.
There will be no boots on the ground in Syria. There will be no open-ended commitment. There will be no assuming responsibility for another country's civil war.
These and other differences with Iraq are the exact reasons why many members of Congress who opposed that war and voted against it are supporting this action against Syria today.
So what is Syria? It would be a tailored action to make clear that the world will not stand by and allow the international norm against the use of chemical weapons to be violated with impunity by a brutal dictator willing to gas hundreds of children to death while they sleep. Our action would be a limited and targeted military action, against military targets in Syria, designed to deter Syria's use of chemical weapons and degrade the Assad regime's capabilities to use or transfer such weapons in the future.
So what's at stake here that caused the President to come to the Congress and ask Congress to authorize action?
Those of us who believe in the international order and believe in efforts to ensure that certain international norms against chemical weapons are respected -- we have much at stake in this debate.
For nearly 100 years, the world has stood up for an international norm against the use of chemical weapons.
There's a reason why the United States joined the Geneva Conventions. There's a reason why the United States and 98 percent of the world are signatories to the Chemical Weapons Convention. The reason is this: our nation is safer when these norms are strong. Our interests are protected when these weapons cease to exist. Our allies and partners are protected when these threats are reduced.
The world agrees with us: chemical weapons were used in east Damascus on August 21st. Dozens of countries or organizations around the world acknowledge the use of chemical weapons in Syria, and of those, many have said so publicly. Many countries or organizations have also stated in public or in private that the Assad regime is responsible. And we continue building support around the world every day.
As part of that effort, this weekend I will meet with European Foreign Ministers in Vilnius, Lithuania, where I will continue to lay out the evidence we have collected and seek to broaden support for a limited military response to deter the Assad regime from launching another chemical weapons attack.
Let me be clear: I have no doubt that Assad will use chemical weapons again and again unless we take action.
I have no doubt that we will never get to the negotiating table for the peace talks we have pushed for if Assad believes he can gas his way out of his predicament, just as we'd never have gotten to the peace talks that lead to the Dayton Accords if military action hadn't been part of the equation.
I have no doubt that if we look the other way, we risk not only Assad's repeated use of chemical weapons within Syria, but downstream consequences for our allies and friends in the region including Israel, Turkey, Jordan, Lebanon, and Iraq.
When I hear firsthand about panicked parents in Israel rushing to buy gas masks for their children, I am reminded of so many who live so close to Assad's reign of terror.
And I have no doubt that for anyone who wants to see a diplomatic solution to two of the world's most pressing proliferation challenges -- Iran and North Korea -- ask yourselves: Are these two countries more or less likely to plunge ahead with proliferation and provocation if they see Assad's actions go unanswered? I would argue that we all know the answer to this question: They are more likely to do so.
The costs of inaction here are much greater than the costs of action.
Some people have asked why we would consider acting without the backing of the United Nations Security Council.
It's the same reason that President Clinton in Kosovo did not bind his conscience to a Russian or Chinese veto in New York: In Kosovo, without a single American combat casualty, countries of conscience acted and the world is a better place because we did.
It was the right thing to do then, and it is the right thing to do now.
We already know who used chemical weapons. We know when they were used and how they were used. We wish the United Nations today were in a position to defend these norms rather than being blocked from acting by Russian and Chinese obstruction -- because we believe in the institution.
But we also believe in the principle that we cannot turn our backs and say there's nothing we can do. We cannot allow these weapons to be used to slaughter innocents with impunity.
This is a vote of conscience. And I know that the same reasons that compelled me to join the United States Navy and serve, and the same reasons that compelled me to speak out against the war in which I'd fought, tell me now that the cause of conscience and conviction is the cause for action in Syria.
John Kerry, a Navy veteran and former U.S. Senator from Massachusetts, is the 68th Secretary of State.