The killing is a game-changer that will divert America’s attention from other priorities and force Trump to send more troops and weapons to the Middle East rather than withdrawing.

Protected by the vast Atlantic and Pacific oceans, the American homeland is a difficult target for direct retaliation. Iran and its proxies have easier marks around the world.

The Trump administration owes the world a clear explanation of how it justified an operation to kill Iranian Gen. Qassem Soleimani. So far, the strike seems legally dubious, if not flagrantly illegal.

Britain, France and Germany have shifted their position, but with the suggestion of permanent denuclearization in exchange for permanent removal of sanctions, Iranian Foreign Minister Javad Zarif may have kicked the ball back to the United States.

After recent military confrontations, the Strait of Hormuz is likely to become the center of a critical competition whose outcomes affect the global oil market. Asian countries, in particular, should be pushing for an end to Trump's "maximum pressure" policy.

The recent US cyber-attack on Iran, in retaliation for the downing of its drone, raises new questions for the militarization of cyberspace: what are the norms governing cyber war? What are the implications for international cooperation on the global Internet? How can governments stop cyber-attacks from escalating in unpredictable ways? These matters greatly concern the US and China.

Starting in May, the White House hopes to extinguish Iran’s oil exports. However, any destabilization may prove counter-productive and cause long-term damage to the United States, the region, and global prospects.

Trump’s second State of the Union address demonstrated his determination to pursue his America First policy, especially on trade, but also on security. A clear preference for bilateral deals and peace through strength and primacy are key elements in his strategy.

Iran has proven resilient against American efforts to damage it.

Trump’s Iran sanctions are opposed by the rest of the world and will only serve to exacerbate conflict.