Lieutenant commander in the context of "Lieutenant (navy)"

A senior officer is an officer of a more senior grade in military or other uniformed services. In military organisations, the term may refer to any officer above junior officer rank, but usually specifically refers to the middle-ranking group of commissioned officers above junior officer ranks but below flag, general or air rank. In most countries, this includes the ranks of lieutenant commander/major/squadron leader, commander/lieutenant colonel/wing commander and naval captain/colonel/group captain, or their equivalents. In some countries, it also includes brigadiers and commodores.

Sometimes, particularly in the army, this grade is referred to as field-grade officers, field officers or officers of field rank. Historically, a regiment or battalion's field officers made up its command element.

Erik Samsel Kristensen (March 15, 1972 – June 28, 2005) was a lieutenant commander of the United States Navy SEALs who was killed in action during Operation Red Wings. He and several other SEALs set off as part of a search and rescue mission, hoping to assist a four-man SEAL team that was engaged in a firefight with Taliban fighters.

Squadron leader (Sqn Ldr or S/L) is a senior officer rank used by some air forces, with origins from the Royal Air Force. The rank is used by air forces of many countries that have historical British influence.

Squadron leader is immediately senior to flight lieutenant and immediately below wing commander. It is usually equivalent to the rank of lieutenant commander in the navy and of the rank of major in other services.