Rubuta ci gaba don wannan sakin layi - Don ayyukansa a wannan yaƙin Forbes ya sami ci gaba zuwa kyaftin a ranar 25 ga Yuni, 1803, kuma ya kasance a cikin garkuwar har zuwa 1811, lokacin da aka zaɓi rundunarsa don shiga cikin mamayewar Java
A shekara ta 1811, a karkashin Sir Samuel Auchmuty. An sanya shi a matsayin kwamandan kamfanonin flank na rundunonin Birtaniya daban-daban, kuma a kan jagorancin su ya jagoranci hare-haren a kan layi a Waltevreede da Fort Cornelis, kuma ya kasance a gaba a kowane gwagwarmaya tare da sojojin Holland. Don waɗannan ayyukan an gode masa sau biyar a cikin umarni na gaba ɗaya, ya karɓi lambar zinare don Java, kuma an ɗaukaka shi zuwa Manjo a ranar 29 ga Agusta, 1811. A watan Mayu na 1812 ya umurci 'yan bindigar na 59 da kamfanonin haske na 78 a cikin wani kamfen don rage Hamengkubuwono II, Sarkin Yogyakarta, kuma a watan Mayu na 1813 ya dakile babbar tawaye da ta barke tsakanin Malays a Probolinggo a gabashin tsibirin Java. A cikin wannan tayar da hankali an kashe Lieutenant-colonel Fraser na 78th, kuma Forbes, a matsayin babban, ya karbi mataki a cikin gabatarwa a ranar 28 ga Yuli 1814. A cikin 1817 ya koma Scotland, kasancewar shi kadai ne jami'in da ya dawo daga cikin arba'in da biyu, kuma ya kawo tare da shi talatin da shida daga cikin ɗari biyu da ɗari biyu. Ya tafi rabin albashi kuma ya zauna a Aberdeen, inda ya rayu ba tare da wani aiki ba har tsawon rayuwarsa. A ranar 10 ga Janairu 1837 an daukaka shi zuwa colonel, a 1838 ya zama CB, kuma a 1846 ya zama babban janar.