A defense contractor is cutting about 170 jobs in Thousand Oaks as it shutters a facility that made signal jammers to prevent IED attacks during the Iraq war.

McLean, Va.-based ITT Exelis’ electronic systems division operated a factory with about 215 employees on Willow Lane in Thousand Oaks. About 45 of those workers will be reassigned to a facility in Van Nuys, but the rest will be laid off. The cuts will begin next April and play out over the course of 2012, company officials said.

The move comes as the United States prepares to withdraw its forces from Iraq as laid out in a 2008 agreement.

“These are difficult decisions that have to be made,” said Tim White, a spokesman for the ITT Exelis electronic systems division. “There’s a strong headwind in the defense industry as the war comes to a close. There are bills that have to be paid at a national level. The military feels that they have enough of these IED-jamming devices.”

The work force in Thousand Oaks manufactured devices that could jam the cell phone signals that Iraqi insurgents used to detonate improvised explosive devices, or IEDs. The makeshift bombs, often set as traps along roads, became a defining weapon of the war because they turned every supply convoy and troop movement into a potential combat situation.

At the peak of production during 2005 and 2006, the Thousand Oaks factory was producing up to 1,250 units a month, White said.

“Quite honestly, the folks that worked there in Thousand Oaks really helped turn the tide and did tremendous work for our soldiers,” White said.

ITT Excelis’ contract with the armed forces was open-ended to allow the military to scale up and down its orders as needed. It started with a value of $700 million but ended up being worth about $1.7 billion, White said.

ITT Excelis is a pure play defense contractor, meaning its only customer is the government. But both pure-play defense contractors and those with commercial divisions are cutting back.

In Goleta, Raytheon cut about 160 jobs. Thousand Oaks-based Teledyne Technologies cut early and deep, shedding about 700 employees during 2009. It has since regained most of its headcount, however, through the acquisition of a commercial and industrial sensor company.