The killing of top Iranian general Qasem Soleimani in Iraq on the orders of U.S. President Donald Trump has intensified regional uncertainty, sparked fears of rapid escalation and left many questions unanswered.

"I think that the question that we ought to focus on is, why now?" presidential hopeful Elizabeth Warren told CNN on Sunday. "Why not a month ago, why not a month from now?"

To many observers the kill order was a shock tactic devoid of a strategy. Skeptical U.S. politicians and analysts have been at pains to describe the Iranian as a "bad actor" while also querying the reasoning behind the killing as well as its legality.

Profile: Who was Qasem Soleimani?

Analysis: Soleimani killing not another Sarajevo incident

Soleimani had been in U.S. sights before – presidents George W. Bush and Barack Obama both opted not to target him, former officials have said – his operational background was widely known and Trump has previously stepped back from taking direct military action against Iran. 

So, why now? There have been several answers from the Trump administration, the most consistent being the claim Iran's powerful military official was plotting "imminent" attacks that would target Americans.

Legal experts differ on whether the killing was lawful, but the imminence of any threat is critical in justifying the act as self-defense. What "imminent" means in this case remains unclear. 

Chairman of the Joint Chiefs of Staff Mark Milley has said Soleimani planned a "significant campaign of violence" against the U.S. in the coming days, weeks or months.

Observers have asked, where's the evidence? The New York Times reported officials as saying the underlying intelligence behind the justification for the killing was "razor thin." And if Soleimani was planning acts which posed an imminent threat to Americans, would his death end it?

Yale Law School professor Oona Hathaway tweeted on Saturday that the strike was "legally tenuous under both domestic and international law" and has followed up with lengthy critiques of the decision and subsequent threats tweeted by Trump.

U.S. Secretary of State Mike Pompeo, on a tour of the Sunday political shows, spoke in generalities about the situation and repeated a claim that Trump's hardline approach towards Iran was necessary after eight years of appeasement from the Obama administration.

"We have to prepare, we have to be ready, and we took a bad guy off the battlefield," he told CNN.

One potential reason, implied by Warren, is that Trump took the decision to distract from impeachment and other problems in a "wag the dog" tactic.

Wag the Dog was a 1997 satire, starring Robert De Niro and Dustin Hoffman, in which a White House chief of staff worked with a Hollywood producer to create a fake TV war and distract from a presidential sex scandal. 

"Next week the president of the United States could be facing an impeachment trial in the Senate, we know he's deeply upset about that," Warren said on Sunday. "And I think people are reasonably asking, why this moment? Why does he pick now to take this highly inflammatory, highly dangerous action that moves us closer to war?”

The "wag the dog" theory goes like this: Trump has been impeached, a Senate trial is due over the coming months and the shock order to kill a top Iranian military official is a huge distraction that could also boost his nationalistic base in an election year.

Is the theory really credible?

Similar accusations have been leveled before. In 1998, days after an apology to the American people over his "wrong" relationship with White House intern Monica Lewinsky and in the midst of his own impeachment investigation, Bill Clinton launched military strikes in Afghanistan and Sudan.

The strikes were responses to al Qaeda's bombings of U.S. embassies in Kenya and Tanzania, and Clinton argued they were also designed to preempt future attacks on Americans. Links with scandal at home were rejected, but questions over the timing lingered.

Clinton sent cruise missiles to destroy an Al Shifa pharmaceutical factory in Khartoum and target Osama Bin Laden's base in Afghanistan on the day Lewinsky testified before a grand jury.

Meanwhile Trump's own words from 2011 and 2012, frequently shared online in recent days, appear to confirm that he sees electoral advantage in military action against Iran.

"I've said before, I think Obama will go to war with Iran because I think he views it as good politically," Trump told Fox News ahead of the 2012 presidential election.

"That's pretty sad and it's a pretty sad thing to have to say, but I think he will absolutely go to war with Iran. I think he views that as a positive from a political standpoint, and I think he's just waiting for the right moment."

Warren has broken ranks by making the "wag the dog" insinuations publicly, arguing Trump has previously shown he's prepared to do "whatever he can to advance the interests of Donald Trump." 

Whether or not the claims stick, Trump's decision to authorize the killing of Solimanei - and the consequences of that decision - will now be central to the 2020 campaign.