 As such, service dress uniform is considered less formal than both full dress uniform and mess dress uniform, but more formal than casual wear combat uniform.Service dress uniforms were originally worn on active service in the field or at sea, but became relegated to office, barracks, and walking out dress as more practical field uniforms evolved.In some parts of some armed forces such as the British Army, service dress uniform may also be used for ceremonial occasions, gradually replacing in this role the full dress uniforms that had preceded them as field uniforms.