Janus is named after the Roman god of portals and doorways, who presided over the beginning and ending of wars. It is the name for a family of related computerised combat simulation systems originally developed in the US and adopted by a variety of countries including Britain, France, Australia, Canada, and New Zealand. Janus was widely used for over four decades and influenced the development of many simulation systems still in use today such as JCATS and OneSAF (Shimamoto 2000 and Berzins 1999).

Janus has been used for many applications including: tactics training, combat leader and team training, historical analysis, operational rehearsal, capability and force structure experimentation, doctrine development, command post exercises and disaster relief exercises (Schrader 2009, p208).

Between 1990 and 2009, the Australian Army developed a home grown version of Janus, which became known as Janus(AS)1. As in other countries, Janus(AS) was used for capability development experimentation and combined arms team decision training by a wide variety of users. Almost every element of the software was adapted in some way to suit Australian user requirements. However, few of these modifications were published beyond the forum of the international Janus User group or the immediate development team.

When the Australian Army made the decision in 2003 to follow the US Army and phase out Janus, promotion of Janus(AS) developments was actively inhibited and few people even understood that there were significant differences. The final years of Janus(AS) usage were characterised by misinformation, ambivalence, ignorance and occasional malice. As the incumbent and leading simulation software for over 20 years it was advantageous for those advocating alternatives to actively undermine the software. It was often convenient to conflate the Australian version with its various US relatives and emphasise how old the software was rather than highlight the many upgrades that had been made.

The Army Simulation Campaign Plan (ASCP) of 2011 directed that “Janus” be withdrawn in 2011 and replaced by OneSAF. However, Janus(AS) remained in service until 2016 and was ultimately replaced by JCATS, itself a derivative of the original US version of Janus. It is not without irony that the final reference incorrectly uses the generic label “Janus” instead of the more accurate “Janus(AS)”. It is, however, sad that the final footnote brushes aside a project that had delivered so much for so long to the Australian Army.

The local enhancements to Janus(AS) were a direct result of user requests and implicitly represent a significant body of user requirements for constructive combined arms simulation. While the specific implementations in Janus are no longer relevant, the problems they were attempting to solve may well be. Janus(AS) also represents the work of hundreds of people who contributed to defining requirements, implementing models, testing the system and then using it for education and research.

The following notes are an attempt to recover some of the baby that was hastily discarded along with the bath-water.

Technical Overview

Functionality Overview

Technical Change Reports

Suppression Model

Acedemic papers and other references for Janus .

1. At the time, “AS” was the NATO code for Australia (Austria having taken AU). It was not until 2004 that NATO switched to the ISO codes and “AU” became the code for Australia (AT being Austria and AS American Samoa) and these are of course now the country codes used for internet URLs. See https://en.wikipedia.org/wiki/List_of_NATO_country_codes and https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2


V. Berzins, V., Luqi, Shing, M., Saluto, M., Williams, J. 1999. Re-engineering the Janus(A) Combat Simulation System. NPS-CS-99-004. US Naval Postgraduate School. Monterey, CA. http://www.dtic.mil/dtic/tr/fulltext/u2/a360817.pdf

Shimamoto, Faith. 2000. Simulating Warfare is no Video Game. Science and technology Review. https://str.llnl.gov/str/Shimamoto.html

Shrader, Charles R. 2009. History of Operations Research in the United States Army, V. 3, 1973-1995. Office of the Deputy Under Secretary of the Army for Operations Research, United States Army: Washington D.C.

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