Peshmerga forces opened a new, northern front on Thursday in the offensive to retake Mosul from the Islamic State (IS) militant group, which is putting up a determined defense and inflicting significant casualties.A variety of Iraqi security forces have already been pressing toward Mosul from the east and the south since Monday, when Prime Minister Haider al-Abadi declared an official start to the Mosul liberation campaign.Now the north is in play. In an official statement Thursday, the …