What is antifa and why is Trump targeting it?

US President Donald Trump has signed an executive order that declares the anti-fascist antifa movement a domestic “terrorist organisation” as part of a crackdown on what he claims is left-wing sponsored political violence. Here is some background on the movement, and why it might be difficult for the Trump administration to follow through on its threatened crackdown: Trump vowed to take action against left-wing groups he accuses of fomenting violence after the murder of conservative activist Charlie Kirk earlier this month. There is no public evidence tying antifa to Kirk’s assassination. The motive behind the shooting remains unknown, and the accused gunman, Tyler Robinson, is not cooperating with investigators, officials have said. Still, Trump has described antifa as a "sick,...