In the five years following the War of Independence the UNION experienced a huge surge in economic and industrial growth. During this period the leaders of the army reviewed the future organisation of the army and its equipment and the government considered the UNION's future relationship with the rest of TIAN.
Engineers at the Rock Island Arsenal had prototyped a new field gun based on the best features of the foreign weapons purchased during the War. The new gun proved far superior in all respects to those weapons and it entered full production. In addition development of both a new heavy artillery gun and a heavy towed machine gun had been completed and production started. The UNION companies of Colt, Remington and Winchester had developed a new lever action rifle with a ten round magazine and a six shot revolver both of which had again proven in tests to be far superior to any of the foreign made weapons then used by the army. These new guns also started full scale production. Construction of vehicles and heavy equipment by Studebaker, Abbot Downing and Murphy also continued apace with several new wagon and trailer types entering service.
Additionally the organisation of the army was considered. Originally it had a regimental basis with each army being a self contained force but only capable of operations as a whole. Although this had proven broadly adequate during the War of Independence senior officers realised a different structure was necessary for the future. It was decided to reorganise the army into independent self contained arm of service battalions which would be grouped together into brigades, similar in size to other nations divisions, with four Infantry brigades and one Cavalry brigade forming each army. ( This revision was implemented in the Woodscrew Army several years ago.) In addition the government created the Army Support Service. This body was formed to provide supporting services to the field armies. Members of this organisation would not only man the Rock Island Arsenal and its associated warehouses of stockpiled weapons, ammunition and equipment but also provide the services needed to operate the various army bases including training of new recruits. It was decided that employment in the Army Support Service would be open only to retired army personnel and those who had left the service after a period of enlistment. By this time service in the army, although voluntary, had become very popular with young men in the UNION. However, not surprisingly, many did not see army service as a career but were happy to serve for maybe the minimum time of six years. The Army Support Service provided continuity of employment and the opportunity to develop a trade. Towards the end of this time frame it was also decided to create a fifth army which would be based at the new Fort Bridger near Tucson, a little north of the border with Mexico.
This decision was prompted by concerns in the UNION government about the situation in Mexico.
For some years a low level insurgency had been going on in Mexico between the government and Arab supported religious terrorists in the south of the country. The terrorists were keen to create a fundamentalist nation in Mexico similar to those in the Arab countries of Syria, Iran and Iraq. This insurgency had been simmering for a long time but had increased in strength over the past few years. Mexican government troops and police were finding it increasingly difficult to control terrorist activities and the fundamentalists were striking government targets over widening areas of the country and with increasing success. Although at that time the Mexicans had not asked for UNION support, it had been decided to offer, free of charge, the redundant foreign made military equipment available as a result of re equipment of the UNION army with home produced weapons. This equipment was welcomed by the Mexicans.
The UNION government remained very concerned by the situation in Mexico for other reasons too. It had been realised that following the War of Independence the UNION had no friends amongst other nations in TIAN. Although the UNION could and would remain a self sufficient country it was recognised that Mexico provided a useful pipeline to the rest of the world. To that end the UNION had established its one and only embassy in Mexico City and to support the rather weak Mexican economy had started to import raw materials despite the UNION being quite self sufficient in all such materials.
In the fall of 1866 the Mexican government finally formally requested UNION assistance in the fight against the fundamentalist terrorists in the south of the country. This request was immediately agreed by the UNION and so started UNION army involvement in Mexico that continues to the present day.