The Department of Defense announced Wednesday that Cerner had been awarded a coveted $4.3 billion, 10-year contract to overhaul the Pentagon's electronic health records for millions of active military members and retirees.

The award to the Leidos Partnership for Defense Health — which includes Cerner, an electronic-health-records manager; Accenture Federal; and Leidos, a government contractor based in Reston, Va. — was considered an upset among industry experts. Many had predicted that the bid anchored by Epic Systems, considered a titan in the medical-records field, would land the contract.

Over its potential 18-year life, the contract could be worth just less than $9 billion, officials estimate.

The partnership will be responsible for upgrading and managing the Pentagon's health records for 9.5 million beneficiaries at about 1,000 sites including U.S. clinics and hospitals, and some of the most challenging and remote health-care sites in the world, including in Iraq and Afghanistan.

"The Leidos Partnership for Defense Health is honored to have partnered with the Military Health System for nearly three decades, and we are committed to continuing our work in support of its mission to improve the health and medical readiness of our military," a spokesman for the partnership said in a statement. "Our team stands ready to lean forward with the DoD to implement a world class electronic health records system."

The announcement caps an acquisition process that spanned two years and challenged Pentagon officials to consider a wide array of factors in their vision for a new system: heightened cybersecurity; ease of use for physicians; and the concerns of outside critics about entering into a long-term contract at a time when the electronic-health-records industry is changing rapidly.

"We have taken the time to do this job right," said Frank Kendall, the undersecretary of defense for acquisition, technology and logistics. "If you don't get the contract right, you're going to set yourself up for problems later on."