Horden joined the Royal Australian Navy in 1987 serving in both Oberon and Collins class submarines. He served in the commissioning crew of HMAS Collins and later as Executive Officer of HMAS Farncomb. He completed the Submarine Command Course in the Netherlands in 1999 and assumed command of HMAS Sheean later that year. Since leaving the RAN, Horden has spent more than 20 years as CEO of four high technology companies.