His initial posting was to 5/7 RAR (Mech). During this posting he fulfilled the appointments of Mechanised Platoon Commander, Training Officer and Company Second-in-Command as both a Lieutenant and Captain.

Further regimental appointments in 5/7 RAR (Mech) included Adjutant (2000) and Officer Commanding both Support Company (2001) and Bravo Company (2002). Lieutenant Colonel Forbes has served in East Timor twice with 5/7 RAR (Mech) - 1999/2000 and 2002/2003.

Lieutenant Colonel Forbes' instructional appointments include a position as the Mechanised Infantry Officer Instructor at the School of Armour (1998/1999) and employment as the Infantry Officer Instructor on the Combat Officers Advance Course (2003/2004).

Lieutenant Colonel Forbes completed the Australian Command and Staff Course in 2005, where he was awarded the Land Operations Prize as the course member who achieved the best overall result in the Land Operations module.

Lieutenant Colonel Forbes's staff experience includes Brigade Major (2006) and Chief of Staff (2007) of the 1st Brigade. Lieutenant Colonel Forbes received a Chief of Army Commendation for his performance in these two positions. Further staff appointments included SO1 Coordination in the Office of the Chief of Army (2008) and SO1 Military Commitments-Army (2009/2010). Lieutenant Colonel Forbes assumed command of 5 RAR (Mech) on the 17th of January 2011.

Lieutenant Colonel Forbes has been married to Melissa since 1994 and they have two children, Shamus (2001) and Mackenzie (2003). Lieutenant Colonel Forbes is interested in most sports including running, rugby and cricket.