William Theodore Castle

Successor to Lord Terrence Hood, was Chief of Naval Operations up until his retirement, and became de-facto head of the UNSC during a period of growth for the UNSC, and continued conflict with the Covenant Remnant. His short retirement ended with a return to command as part of the counter-attack against the resurgent Covenant. 
Starting as an officer alongside many up and coming officers, including his close friend Galia Meir, Castle looked to be fast tracked to a role in Navy logistics, but the death of his husband lead to his decision to become a warship commander. Known as a keen logistician, and with a keen eye for talent, he's nurtured a new generation of officers.