He authorized killing Soleimani if there is an imminent threat of him blowing up embassies in the future.....
The intelligence agencies checked with him when they had knowledge of imminent attacks, and he gave the go ahead
This is really a pretty easy explanation.....
That's not what the article claimed was the red line. It said if Soleimani planned to " kill Americans " he could be taken out since as long ago as 7 months . Considering the presence of so many Americans in the near two decade war zone AKA Iraq it seems ridiculous that the bar was set so low for the assassination of the Iranian general.
The article also paints , imo , a very one sided account of US /Iranian relations since Trumps decision to scupper the nuclear deal and initiate crippling sanctions that are , if we are being honest here , acts of economic and diplomatic warfare designed at causing widespead suffering to the people of Iran.
The theme runs something like US economic and diplomatic warfare is portrayed as " pressure " whereas their reactions to it are aggression. We should be mindful that the Trump actions to attack Iran are ultimately responsible for everything cited in the article and stuff not cited like the deaths of those killed as a result of protests in Iran over months , the attacks in Iraq by both sides along with those of the plane downing with probably much more to follow