A limited duty officer (LDO) is an officer in the United States Navy or United States Marine Corps who was selected for commissioning based on skill and expertise. They are the primary manpower source for technically specific billets not best suited for traditional Unrestricted Line, Restricted Line, or Staff Corps career path officers. Per Title 10, U.S. Code, an LDO is a permanent commissioned officer appointed under section 8139 in a permanent grade above chief warrant officer, W-5, and designated for limited duty. Role LDOs perform tasks similar to those of warrant officers (WO), but the formal definition differences are subtle and focus on the degree of authority and level of responsibility, as well as the breadth of required expertise. The term "limited duty" refers not to an LDO's authority, but rather the LDO's career progression and restrictions. Prior to World War II, a LDO could only advance as far as lieutenant (O-3E) in the Navy and captain (O-3E) in the Marine Corps. In later years, an LDO could be promoted to commander (O-5); in the Marine Corps, the senior LDO rank is lieutenant colonel (O-5). In the 1990s, the ceiling in most U.S. Navy LDO communities was raised to captain (O-6). The LDO/CWO motto is "sursum ab ordine" which means "up from the ranks" to underline a distinction between LDOs and CWOs and those Naval and Marine Corps officers commissioned directly from collegiate programs such as the United States Naval Academy, United States Merchant Marine Academy, Naval ROTC and Marine Corps Platoon Leaders Class, and similar post-collegiate pre-commissioning officer candidate programs of the Navy and Marine Corps such as Officer Candidate School and the former Aviation Officer Candidate School. Command Unlike their unrestricted line officer (URL) brethren, most LDOs in the U.S. Navy cannot aspire to command a major warship, combat aviation squadron, or auxiliary vessel, although for a select few in the right communities, command is now a possibility, particularly command of shore installations and technical training schools. In the U.S. Marine Corps, some military occupational specialties (MOS) permit LDOs to be commanding officers. Many LDOs have qualified for command ashore of certain shore activities, ranging from activities such as small to medium-size Navy Operational Support Centers (formerly "Naval Reserve Centers") and Naval Support Activities at the lieutenant commander and commander level, to large activities such as the Naval Air Technical Training Center at the captain level. In