Militants from the self-proclaimed Islamic State (IS) militant group attacked the Hamrin oil field late Monday night, killing four guards and setting multiple wellheads on fire.The attack highlighted the IS group’s ongoing ability to launch guerrilla-style attacks in a swath of territory in northern Salahaddin and Diyala provinces, which Iraqi security forces have ostensibly controlled for more than a year.The Hamrin field, in Salahaddin, is being guarded mainly by paramilitary groups op…