Game changer.

That is the best description of President Trump’s decision to order the drone attack on Iranian Major General Qassim Suleimani. The U.S. is entering unchartered waters. This requires taking a step back and asking how this impacts American national security and Middle East geopolitics.

We take note of the muted, stony silence, reaction of the Arab world. There has been no rush in Middle East capitals to condemn the U.S. or Israel. That is distinct from the Iranian reaction, which has focused on both countries. Even criticism in Europe has been restrained.

There is little disagreement regarding the role Suleimani played in developing and implementing Iranian military aggression. More than that, he was considered a possible successor to President Hassan Rouhani and enjoyed significant support and popularity.

The Trump administration believes Suleimani responsible last week’s attack on the American embassy and directly suggested Suleimani was planning further attacks against U.S. targets or American allies. For those reasons, the administration believed Suleimani was a legitimate target.

However.

Killing a state actor is a fundamentally different proposition than ordering the killing of a non-state actor. In the post-9/11 world, nation states such as the U.S. and Israel have engaged in aggressive operational counterterrorism targeting groups such as al-Qaeda, the Taliban, Hamas, Islamic Jihad and Hezbollah. Killing Suleimani is not akin to killing Osama bin-Laden. The two cannot be equated.

Drone attacks have been conducted against leaders, planners and implementers of terrorist attacks. The use of drones has been justified under the umbrella of the international law principle of self-defense and articulated as preventive self-defense.

While subject to criticism, it is, a widely applied means of engagement. Critics point to “blow-back,” that while killing a terrorist may prevent an impending attack it heightens the odds of future terrorist action. Furthermore, critics point to the unintended killing of innocent individuals as cause for deep concern. Both criticisms are legitimate and demand attention of decision makers.

Be that as it may, the attack on Suleimani represents something quantifiably different.

In attacking an Iranian major general, the U.S. attacked Iran. We need to be cognizant of the fact this is not “just another attack” against yet another terrorist. To view the killing of Suleimani through that lens is to miss the most important aspect of President Trump’s decision.

Until this past week, Iran and the U.S. have been engaged in an increasingly amped-up rhetorical back and forth. Both sides have engaged in mutual acrimonious, threatening, and jingoistic language largely related to Iran’s efforts to develop nuclear capability.

President Trump did what candidate Trump promised to do: withdraw from the nuclear deal initiated by President Obama.

Trump has been consistent in articulating what he perceives to be the threat Iran poses to regional stability and world order. While he never drew the awkward and thoroughly gratuitous red lines that Israeli Prime Minister Netanyahu did regarding Iranian nuclear development, or that President Obama did regarding Syrian President Assad’s use of chemical weapons, he was similarly bellicose in language.

Neither Netanyahu nor Obama delivered on their promises. That is not the case with President Trump. Supporters would propose he did as promised; opponents would argue there was no need to move from words to action.

But as that is exactly what happened we need to consider the consequences and possibilities. We have crossed the Rubicon; there is no turning back from the fact the U.S. deliberately attacked a state actor and openly acknowledged this undertaking.

The deed is done. The game has changed.

Now the hard part, for we are entering a new game with unclear rules and uncertain norms for we have, possibly, put mere words in the back seat. The caveat reflects the immediate Iranian reaction: strong words, threatening a response, and three days of national mourning.

That suggests two things: surprise at the U.S. action and the need to carefully consider their next steps. Rather than impulsively lashing out, Iranian leadership seemingly has allowed itself to take a deep breath, whilst engaging in tough language. Obviously, the two are not at odds; they can be understood as working together.

One assumes American national security officials understand the proverbial apple cart has been turned upside down. The questions, for which there are no answers but demand our attention, are whether Iran will respond militarily (on whatever level) and what will be the U.S. response.

Or, will the Iranian leadership “take a hit,” acknowledging a line has been crossed but recognize there is grave danger in an additional crossing of that line.

How these two questions will be answered in the days ahead will enable us to better understand whether there is a “grand strategy” in play, whether this was only a tactical decision, or whether, as Huxley wrote, we are entering a strange new world.

Regardless of the answer, the game has changed.

Amos Guiora

Amos N. Guiora, J.D., Ph.D., is a professor of law at the University of Utah’s S.J. Quinney College of Law and the author of “Populist and Islamist Challenges for International Law.”