President Trump's decisive action in launching a missile strike against Syria has put the world on notice that the U.S. will not shy away from using force to achieve its goals. That has been a matter of some concern in recent years in light of Syrian dictator Bashar Assad's history of atrocities, saber-rattling by North Korea, and increasingly aggressive behavior by Russian military against western countries.

The questions Trump must answer now: What are U.S. goals in the region, and how far is this nation willing to go to in their pursuit? Sending 59 Tomahawk cruise missiles into Syria on an hour's notice sends an unmistakable message that this nation will not stand by while Assad assaults his people with a banned nerve agent. It also is a complete reversal of Trump's earlier expressed intention to stay out of conflicts in Syria.

Whether he acknowledges it or not, Trump has drawn his own version of President Barack Obama's infamous "red line." He also has gotten a quick lesson in just how hard — and perhaps unwise — it is to back this country away from its leadership position on the world stage. U.S. strategic interests extend far beyond its borders. Allowing Assad to get away with yet another gas attack, this one in blatant violation of a 2013 agreement to abandon chemical weapons, would have sent a dangerous signal not just to Assad, but strongman regimes around the world that there was little consequence for flagrantly violating international norms.

There is an implied "or else" in Trump's statement that the U.S. will not tolerate further infractions. It is imperative that he articulate expectations and the options under consideration. Reacting to the footage of children convulsing and foaming at the mouth as they die from the effects of Sarin nerve gas is understandable and even necessary, but it must be followed by a measured strategy that he can take to Congress. In the Minnesota delegation, Rep. Jason Lewis and Rep. Tim Walz have said they support the missile strike, but that further military action by the administration must be authorized by Congress. The Star Tribune Editorial Board agrees.

As he settles into his new role, Trump appears finally to be ready to abandon campaign rhetoric and chart his own course. After an ill-­considered initial reaction to the Syrian chemical attack in which he blamed Obama, Trump now says the responsibility for action is his. That is a welcome acknowledgment, but he should bear in mind it is a shared responsibility that draws on the finances, support and even the lives of Americans who may be called to fight and die to carry out his objectives. His unilateral strike aside, Trump now must begin a leader's most difficult work: explaining to the public his rationale and intentions and building support for his course. Otherwise, the effectiveness of a sudden show of U.S. might is undercut and allies may doubt American resolve.

He will also have to show that in addition to exercising power, he is capable of diplomatic restraint. Russia's response is disturbing, especially its decision to sever an air safety agreement to share coordinates and flight information with the U.S. that was intended to minimize the chance of accidental conflict in the region. It was this "deconfliction" line that was employed in advance of the U.S. strike, allowing Russians to move nearly 100 troops and materiel out of harm's way at Shayrat airfield.

Removing that line raises the danger of a proxy war, given that Russia controls Syrian airspace and has troops embedded throughout the country. Trump administration officials who paint Russia as either complicit, incompetent or pawns of Assad are unhelpful, particularly in advance of Secretary of State Rex Tillerson's visit to Moscow next week. If Assad is to give up power, Russia will have to play a role.

This is a region whose politics are fiendishly complicated and bedeviled by multiple factions. If Trump is to purse Assad's ouster, he must work with other nations to develop a plan that prevents Syria from falling into chaos and becoming an even greater source of instability.