James Matthews, US correspondent, says: On retaliation, the question for Joe Biden will be how “huge” does it have to be.
So far, we have seen a measured US response to attacks, facilitated by the fact that they hadn’t cost American lives.
That’s changed.
Deaths of US service members – first and foremost a tragedy for those concerned – represent an affront to the American sense of global authority and influence over global events.
It raises questions about Mr Biden’s judgement and amplifies criticism that he has been too restrained in his response to relentless aggression.
His challenge is to see beyond his next move.
A president plugged into the region, his friends and enemies, will have a prior sense of how far retaliation needs to extend.
The Americans will look to human and technical intelligence in an effort to establish whether there was direct Iranian involvement and instruction.
That same intelligence has led US officials to believe, until now at least, that Iran doesn’t want direct conflict with the US – that it sees the danger it would present.
Tehran, however, has been untroubled by the work of its proxies. That’s the issue Mr Biden needs to address.
In doing so, we’ll find out whether his principles on retaliation apply to America itself as much as its allies.
Watch: How should the US respond to strikes? Wilfred Frost hears the view of security analyst Jonathan Paris…
