Saudi Arabia is escalating a security crackdown to defend against what the kingdom’s rulers see as a growing legion of threats arising from regional instability.

When President Barack Obama arrives in the kingdom later this month for talks with King Abdullah, he will encounter officials more preoccupied than ever with what they perceive as the growing peril from both Shiite Muslim Iran and its allies, as well as from Sunni Muslim fundamentalist groups such as the Muslim Brotherhood.

In the monarchy’s latest measure to prevent unrest abroad from rebounding back to the kingdom, authorities have given Saudi fighters in Syria and elsewhere a two-week deadline to return home and turn themselves in. […]