The situation and implications following the killing of General Qassem Soleimani and Iraqi militia leader Abu Mahdi al-Muhandis by the USA on 03 January 2020 are still unclear. The following is a personal opinion based on some experience and the 'open source' information available.
This assassination will significantly damage Iran's capability atleast in the short term - the General was a very well connected (successful) strategist and leader but I understand also a micro manager; this could make him a 'difficult act to follow'. There is a growing public expectation for Tehran to respond to this incident (if only to save face and not to be seen to cower to the USA). The number of people on the streets in Tehran today is indicative of the esteem that the General was held in the eyes of the Iranian public who are calling for revenge.
The response could come in any number of ways and anywhere in the world. It is my opinion that war is not in either parties best interest so it is anticipated they will want to balance the scale of response to maximise publicity but avoid an immediate rush to direct military confrontation.
How?
The response might come in a number of ways (and there maybe more than one response). Ideally a 'spectacular' but perhaps designed to minimise civilian casualties. Supesition but for example only:
A direct attack against a military target in the ME (probably Iraq but for example Bahain or even Qatar which hosts CENTCOM, US Central Command for the ME)
Shipping in the Gulf. Possible mining of the Straits of Hormuz or damage / arrest of transitting vessels. Iran is hosting Naval Exercises with China and Russia this week! (Global oil price impact). The UK is to escort British flagged vessels.
Attacks against 'allied' critical infrastructure. Pipelines, refineries, oil and gas wells. (Aramco again or other?). (Global oil price impact)
Cyber attacks against critical national infrastructure, probably in the USA.
Alliance terrorist group attacks against US military (or other western military interests). There has already been one of these over the weekend (Al Shabab in Kenya) although its unlikely this was directly related to this assassination.
Other...........?
Depending on scale, other options for now might signal a much more sinister escalation. This might include a major attack on a western city, aircraft bomb, holiday spots, dams, bridges, utilities, hotels, conferences etc? Summary executions.
It is understood that the Iraq Government is to vote on 11 January 2020 on a motion that could see US (and associated Allied) troops being evicted from Iraq. Whilst this is probably unlikely, it would be catastrophic for US and western ME policy. Iran could also try to draw China and Russia closer.
When - Iran's response could come at anytime but is unlikely until after General Soleimani's burial tomorrow. That will mark a high point for public outrage, but on a practical front they may need additional time to get assets and supporting logistics in place to mount an attack.
As far as the USA is concerned, and I have not seen this muted anywhere, but what a great smoke screen to take focus off Impeachment and to gather momentum for re-election!? It is not likely to be plain sailing for President Trump at home. He does not appear to have consulted allies or the UN before doing this and nor does he appear to have a broader strategy or policy for the Middle East. The action looks like a knee jerk response to a culmination of events, maybe the attack on the US Embassy in Iraq was the 'straw that broke the camels back'? There are questions of legality and Trump stands to be accused of war crimes if he does attack the 50 x cultural sites in Iran he says he has targeted. For now UK and European allies appear to be generally encouraging restraint and de-escalation.
So What?
Overlanders / travellers and businesses should be especially vigilant in the coming days. It is recommended that:
Travel to the Middle East should be postponed.
Review security measures and response plans. Conduct training and exercises to validate plans.
Consider suspending all non essential business travel for the next 7 days (and then review).
Stay away from large public gatherings or popular venue's frequented by Westerners (for example sporting events, theatres, bars and restaurants).
Be prepared for loss of utilities and have plans in place to contact family to assure them of your well being in case of an incident. This will reduce the workload for authorities after an incident.
In the event of mobile phone network overload or shut down, remember that text, applications like 'Whats app' or email may still work. Keep satellite phones charged.
Keep your 'Grab Bags' with you for the next few days. Overlanders make sure you have sufficient food and prescription medication onboard and keep fuel and water tanks topped up.
Monitor national government travel advice, local and international news channels. register with your Embassy 'in country'.
Stay safe!