Hann Najjar was born in Karemlash, Iraq, to Francis Mansour and Najma Dowd. In 1959 he came to the US to study at The Johns Hopkins University after graduating with honors from the Universities of London and Wales.

In 1965 he joined IBM where he developed TDMA satellite communication system for the US Army's DSCS III program, multiprocessing techniques for the NASA Unmanned Orbiting Multifunctional Satellites, PMFL system for the US Navy's Trident Submarine BQQ-6 Sonar among others.

Subsequently, Hann focused on breaking new ground in developing computer based interactive networks for American Airlines reservations, Bank of America financial services, Master Card point of sales, Medi-Cal health services, and IBM Service Bureau. In 1983 he joined Mitre C3I to support DoD and NATO tactical military satellites and terrestrial based networks. He led the development of the follow-on UHF satellite architecture which resulted in the acquisition of ten satellites for the US Navy and several thousand AMUT and EMUT terminals for the US Army, enabling interoperability and shared space capacity among the Military Services.

This was followed by the development of multiple architectures for high-level interoperability between DoD DSN and NATO IVSN heterogeneous networks using ISDN, as well as survivable communications for the US Army's 5th and 7th Corps field commanders to access the LOCE fusion data collection center, a precursor to NATO BICES.

Hann is a life member of the IEEE, has published widely, holds several patents and invention disclosures, and is the recipient of many distinguishing awards like the IEEE First Prize Paper, IBM Invention Award, Mitre best published papers, and DoD letters of appreciation for effective leadership and commitment to superior performance.

He and his wife, Nohra, are the parents of Michael, David, Steven, Julie and Thomas, and the grandparents of 14 grandchildren.