He then returned to the U.S. in 1957 and served as a faculty member at the Army Command and General Staff College at Fort Leavenworth, Kansas.

He was then recruited by Ambassador Henry Cabot Lodge Jr. to serve as mission coordinator at the Embassy of the United States, Saigon.

[4]: 13  After dawn as U.S. forces cleared the VC in the compound Jacobson heard movement downstairs; he threw down his grenade and called out to the Military Policemen (MPs) in the grounds to throw him up a weapon.

[4]: 32–3 [5][6][7] COMUSMACV General William Westmoreland later presented Jacobson with the AK-47 mounted with a plaque reading "A VC fired this weapon and missed.

"[9] In December 1968 he was appointed assistant chief of staff of Civil Operations and Revolutionary Development Support (CORDS), the U.S. and South Vietnamese pacification program.

[11][10]: 283  He then returned to the embassy staff as assistant for field operations, a vaguely defined role in which he supervised agricultural specialists across the country.

[12]: 82  Jacobson apparently shared Martin's over-optimism about the survival of South Vietnam in the face of the North's 1975 spring offensive, claiming in mid-April that a negotiated settlement was imminent.