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A wounded Syrian child is treated at the Israeli Ziv hospital on Wednesday, August 28, in the northern town of Safed, Israel. About 140 wounded Syrians, who have been fighting across the border from Israel, have been treated in Israeli hospitals since the beginning of the Syrian Civil war. According to the U.N. High Commissioner on Refugees, more than 1 million Syrians have fled to neighboring countries since the beginning of 2013, and three-quarters of that population are women and children.

A Syrian-Kurdish man carries a mattress at sunset at the Quru Gusik refugee camp, east of Arbil, the capital of the autonomous Kurdish region of northern Iraq, on Tuesday, August 27. More than 50,000 Syrian refugees have crossed into Iraq's Kurdish region in less than two weeks as authorities rush to house them in more permanent camps.

Syrian refugees listen to safety instructions at the Quru Gusik refugee camp on Saturday, August 24.

Syrian refugees at the Zaatari refugee camp on Thursday, July 18, near the Jordanian city of Mafraq, near the Jordanian-Syrian border.

The expanse of the Zaatari refugee camp in Jordan as seen from an aerial view on July 18. The camp was opened on July 28, 2012, and is home to more than 130,000 refugees.

Syrian refugee children walk in the Bab al-Salam refugee camp in Syria's northern city of Azaz on Monday, July 15.

A boy walks with jugs of water on June 27 in a neighborhood in Beirut, Lebanon, with a high concentration of Syrian refugees. Since January, the number of Syrian refugees in Lebanon has more than tripled.

Syrian refugees stand with their belongings on June 20, World Refugee Day, at Zaatari refugee camp in Jordan.

A Syrian woman and child look out of a refugee camp window on June 20 in Alman, Lebanon, after fleeing their hometown in Idlib province, Syria.

A child, whose family fled violence in Syria, stands at the Arsal refugee camp on June 14 in Lebanon's Bekaa Valley.

A woman uses a fence at the Domiz refugee camp near Kohuk, Iraq, to dry laundry on May 29.

A boy carries a jug for water at the Maliber al-Salam refugee camp on April 28. The camp, located near the Turkish boarder, houses internally displaced Syrian families.

A makeshift refugee camp is seen near Syria's border with Turkey.

Row after row of temporary shelters fill the Maiber al-Salam refugee camp in Syria's Aleppo province, near the Turkish border on April 17.

Refugees fleeing the conflict in Syria arrive February 18 at the Jordanian border.

A Syrian girl stands at the entrance of a makeshift home near ruins in the ancient city of Serjilla in northwestern Syria on February 11. About half of Syria's refugees are children.

More than 400,000 people have fled Syria this year to countries including Lebanon, Jordan, Turkey, Iraq and Egypt. The Zaatari refugee camp is in Jordan, near the Syrian border.

A refugee collects apples and some bread February 10 at the Azaz refugee camp along the Syrian-Turkish border. Turkey has spent more than $600 million setting up 17 refugee camps, with more under construction.

Clothes dry at the Qah refugee camp near the Turkish border on January 31. Many Syrians are forced to flee with few or no belongings.

A man shows off his pet birds as new Syrian refugees arrive at the International Organization for Migration at the Zaatari refugee camp on January 30.

A refugee child gets a haircut at a makeshift barbershop at the Azaz refugee camp on February 19.

Syrian children gather around women washing in the Zaatari refugee camp on January 31.

A refugee visits a clinic with his child at the Azaz refugee camp on February 10.

Syrians put up tents at the Zaatari refugee camp on January 30.

The U.N. High Commissioner for Refugees supplied tents in Al-Marj, in the eastern Lebanese Bekaa Valley. Some families have endured frigid weather in tent camps or struggle to pay for shelter.

A Syrian girl looks through the window of a bus where she has lived with her family for the past eight months at a refugee camp in Bab al-Salam on the Syria-Turkey border on February 28.

A Syrian jumps across the border between the Syrian town of Ras al-Ain and Ceylanpinar in Turkey's Sanliurfa province on November 10, 2012.

A Syrian refugee waits November 27, 2012, at a hairdresser's shop, where refugees can also receive training, inside the Oncupinar camp in Kilis, southern Turkey.

A Syrian boy attends school in the Turkish town of Kilis on December 17, 2012.

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Editor's note: Rep. Chris Van Hollen, a Democrat, represents Maryland's 8th District. Watch him on "Erin Burnett OutFront" Thursday at 7 p.m. ET.

(CNN) -- Our experience in Iraq provides three essential lessons that should guide America's response to the Syrian regime's alleged use of chemical weapons against its own people.

First, the president must present the American people and the international community with clear evidence that the al-Assad regime was responsible for the use of chemical weapons. The Bush administration took America to war in Iraq based on the false claim that Saddam Hussein had weapons of mass destruction, including stockpiles of chemical weapons.

Those false claims not only led us into a costly and unnecessary war, but did lasting damage to America's credibility. That erosion of credibility is haunting us now, as many in the international community question our claim that the al-Assad regime used chemical weapons. That makes it imperative that the Obama administration present clear and convincing evidence that the al-Assad regime was responsible for the chemical weapons use.

Second, if the Obama administration presents such evidence, it is essential that the United States and the international community take strong action to punish the regime and deter the future use of chemical weapons in Syria or elsewhere in the world. Again, the Iraq example is instructive.

Many would like to forget the fact that the United States and the international community willfully ignored Saddam Hussein's use of chemical weapons against Iran during the Iran-Iraq war and against Iraq's Kurdish population in 1988 in the aftermath of that war.

I remember those days well. Together with Peter Galbraith, my former colleague on the staff of the Senate Foreign Relations Committee, I traveled to the Iraq-Turkey border in September 1988 to investigate Saddam Hussein's chemical weapons offensive against the Kurds. We returned to Washington to urge the United States government to impose economic sanctions against Iraq for its use of chemical weapons.

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While the United States Senate did pass such legislation, it was opposed by the Reagan administration and never made it out of the House of Representatives. Recently released CIA documents demonstrate that the Reagan administration deliberately ignored Iraq's use of chemical weapons because it favored Iraq in its war against Iran. But the failure of that sanctions legislation represented a failure of the United States to help enforce the international convention against the use of chemical weapons.

A strong case can be made that the refusal of the United States and the international community to confront Saddam Hussein for his flagrant violations of the international ban on chemical weapons emboldened him to take additional reckless actions. In 1990, he miscalculated the international response to his invasion of Kuwait.

Years later, even after he had destroyed his chemical weapons stockpile, he underestimated the depth of international concern that he was still hiding them. That is perhaps not surprising, considering that the international community did nothing when Saddam Hussein actually used chemical weapons in the 1980s.

The United States and the international community must not again stand idly by if the al-Assad regime, or another party, has used chemical weapons. It must take action to uphold international norms and send a clear signal that breaches of the international ban on chemical weapons use will not be tolerated.

Failure to act upon strong evidence will only encourage Bashar al-Assad and other international actors to use chemical weapons in the future.

The third lesson from Iraq is equally important as the first two. Our mission must be clearly defined and achievable at an acceptable cost. In 1990, President George H.W. Bush established a well defined goal -- using force to oust Saddam Hussein's forces from Kuwait. He deliberately chose not to send American troops to Baghdad to topple Saddam Hussein, because he rightfully determined that the United States would not be able to contain the violent fallout without a huge commitment of American lives and treasure.

President George W. Bush later made the mistake that his father avoided. The Iraq war clearly established that even massive U.S. troop intervention on the ground for over eight years cannot change many of the basic cultural and sectarian forces at play in the region.

Today, despite the huge sacrifice in American and Iraqi lives, Iraq is rocked by almost daily eruptions of sectarian violence. The American-backed, Shiite-dominated government of Iraq now allows Iranian planes to use its airspace to supply weapons to al-Assad and the minority Shiite Alawite sect that controls Syria.

Meanwhile, al Qaeda and Sunni extremists in Iraq are fighting to defeat the government in Baghdad as al Qaeda and Sunni extremist forces in Syria are fighting in tandem with American-supported rebels to defeat the al-Assad regime. The toxic mix of forces suggests that even a large U.S. troop presence in Syria would be unlikely to change these deep-running currents.

These lessons are important as President Obama defines the purpose of American military action in Syria in response to the use of chemical weapons. The president should make clear that the goal of our military action is to punish Syria for its blatantly illegal use of chemical weapons and to deter the future use of such weapons by the Syrian regime or others that might contemplate their use in future conflicts.

Our action should be coupled with a clear statement that any future use of chemical weapons will be met with increasing force. This goal can be reasonably accomplished by using cruise missile strikes that inflict significant pain and damage on al-Assad's forces without putting American lives in the line of fire.

Some have argued that it is pointless for the United States to engage in punitive military strikes against Syria unless our actions are designed to decisively tip the military balance toward the rebels. That claim downplays the more limited, but nevertheless important, objective of deterring the future use of chemical weapons.

Moreover, defining the success of our response as decisively changing the military balance is unrealistic, unachievable without putting American lives at risk, and will ultimately drag the United States toward full-scale intervention in a Syrian civil war.

Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, has stated that measures like the establishment of a no-fly zone would put American pilots at risk and may not change the situation on the ground.

Measuring success of these actions in terms of changing the tide of the war will lead inexorably to further assertions that American credibility is at stake and suck America into a costly civil war that could, with the current configuration of forces, result in the extremist al Qaeda elements among the rebels gaining the upper hand. That is why it is so important to define this particular mission in a way that can be achieved at an acceptable cost.

Let's heed three important lessons from Iraq: Protect our credibility by presenting clear evidence of the use of chemical weapons by the al-Assad regime; take strong action to punish the illegal use of chemical weapons and deter their future use; and define the mission in achievable terms at a cost we are willing to pay.

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The opinions expressed in this commentary are solely those of Chris Van Hollen.