WASHINGTON — A U.S. Navy office set up less than two years ago to oversee the warfare development of unmanned systems has been eliminated, the Navy said Wednesday.

The Office of Unmanned Warfare Systems — coded N99 in the Navy's system of identifying offices reporting directly to the chief of naval operations, collectively known as OPNAV — is being broken up and its functions distributed to other offices, Adm. Bill Moran, vice chief of naval operations, told service leaders in a Feb. 8 message.

The reorganization, said Lt. Jackie Pau, a Navy spokesperson at the Pentagon, "is the next step in the Navy's ongoing process to mainstream the complementary warfighting effects of manned and unmanned warfare systems."

The move, Moran said in the message, was done "with the goal of creating a leaner, more agile organization."

The N99 office was established in mid-2015 as part of an initiative by then-Navy Secretary Ray Mabus to place unmanned warfare on a par with other OPNAV warfare divisions.

Mabus, speaking at an Oct. 27, 2015, unmanned systems event, lauded the move, calling it "a reflection of the priority that we're placing on this emerging capability and how critical it is that we have cohesive leadership for our unmanned programs."

As with the other warfare offices, a rear admiral was placed in charge, along with Mike Novak, a senior civilian executive. Rear Adm. Robert Girrier assumed his duties as head of N99 in September 2015 tasked, as Mabus said, with the "rapid development, prototyping and demonstration of our Navy's unmanned warfare systems, because those unmanned systems are the platform of the future." But Girrier retired last month without a replacement.

With the breakup of N99, its responsibilities for unmanned integration, accelerated acquisition and oversight are transferred to Rear Adm. Pete Fanta's Warfare Integration Division N9I.

The functions of Rapid Prototyping, Experimentation and Development, Pau said, will merge with Innovation, Technology Requirements and Test and Evaluation N94 under Rear Adm. Dave Hahn.

Current unmanned programs of record, she said, will merge with their respective resource sponsors: Expeditionary Warfare N95, Surface Warfare N96, Undersea Warfare N97 and Air Warfare N98.

Pau noted that "N9I will continue unmanned oversight functions with fellow OPNAV directorates, acquisition program executive officers and the fleet, and will work to accelerate the acquisition of unmanned prototypes within the traditional resource sponsors."

The reorganization, she added, "allows for more complete integration of unmanned platforms and system development across domains."