The Taliban announced the start of their warm-weather fighting season on Tuesday, April 12, vowing "large-scale attacks" in the 15th year of their war against the U.S.-backed Afghan government, the Associated Press reports.

In an email to media, the militants said the spring offensive had begun at 5 a.m. It dubbed the campaign "Operation Omari" in honor of Taliban founder Mullah Mohammad Omar, who died three years ago. The statement said waging jihad against American invaders is a holy obligation.

It said this year's campaign will incorporate suicide attacks, assassinations, and other tactics aimed at undermining the enemy's morale.

The Taliban added that in areas under their control, "mechanisms for good governance will be established so that our people can live a life of security and normalcy." The insurgents control several rural districts and last year seized the northern city of Kunduz and held it for three days.

The Taliban said they would try to avoid killing civilians or destroying civilian infrastructure, and would carry out a "dialogue with our countrymen in the enemy ranks" to try to convince them to join the insurgency.

More than 11,000 civilians were killed or wounded in 2015, according to the UN.

The Taliban have been riven by infighting since Mullah Omar's death became public last summer. Mullah Omar's deputy, Mullah Akhtar Mansoor, had run the insurgency in his name for more than two years and was elected as his successor by a small clique amid mistrust from the rank and file. The dispute has had little impact on the battlefield, however, where the Taliban have advanced on a number of fronts over the past year.