He was posted to Germany in 1998 on a two-year exchange with the Irish Guards, during which time he served as 21C of an armoured infantry company.

In 1999 he saw operational service with the King's Royal Hussars Battle Group in the Former Yugoslav Republic of Macedonia and Kosovo during the air campaign and land deployment respectively. He was awarded a Commander British Forces Commendation in recognition of his service. LT COL Ellwood commanded B Coy, 5/7 RAR on operations in East Timor in 2000. After completing Australian Command and Staff College, LT COL Ellwood served as the Brigade Major of the 1st Brigade for which he received a Divisional Commander's Commendation. LT COL Ellwood subsequently served as the Director Reserves-Army at AHQ prior to assuming command of 5RAR. This occurred at the unlinking ceremony of 5/7RAR on 3 December 2006.

LT COL Ellwood commanded the third rotation of the Overwatch Battle Group (West)OBG(W)-3) on operations in southern Iraq in 2007. OBG(W)-3 was a combined infantry/armour battlegroup consisting primarily of subunits from 5RAR and 2 Cavalry Regiment. He also commanded the fifth rotation of the Timor Leste Battle Group (TLBG 5) in East Timor in 2008 prior to handing over command of the Battalion to LTCOL Huxley in East Timor on 31 December 2008. Jake handed over command of 5RAR during his second operational tour as CO 5RAR.

In 2009, LTCOL Jake Ellwood was awarded the Distinguished Service Cross (DSC) for distinguished command & leadership in action as the Commander of Rotation Three of the Overwatch Battle Group-West during Op Catalyst In Iraq. This was mainly the 5RAR Battle Group Tiger that he commanded.