The Instruction Centre for Operations on Law and Order Assurance (CIOpGLO) is a Brazilian Army facility created in March 2005 in Campinas, Brazil. The mission of this centre involves the offering of training in different perspectives, which includes the preparation of soldiers to enter in slums areas in Rio de Janeiro and other cities to arrest criminals, whenever a federal intervention is required. This centre is involved in training to guarantee law and order and, at the same time, prepare officers and soldiers for interventions even in urban areas. To allow such training, this facility counts with physical built sites to allow soldiers to train how to get inside houses, how to shoot at short ranges (from 0 to 30 meters), how to move and shelter while going up in a hill with many houses and corridors on the way, and so on. The Brazilian Army, in the last few years, started operating in slums like the ones of the "Alemão" and the "Penha" complex in Rio de Janeiro. The Army is also participating in operations out of Brazil in countries like Haiti. In situations like this, the armed forces take over the coordination of public security temporarily to recover the control of certain areas. Since the armed forces were not originally created to act in situations like this, there is a need to train all military stakeholders involved so that the operations are successful. Additionally, major events like the Confederations Cup, the World Cup in 2014 and the Olympics in 2016, generate additional demands for the armed forces, which are likely to be called to act at specific times. Moreover, it is noteworthy that there is a growing trend in which conflicts around the world occur, more than ever, inside the cities, where civilians take great risk and suffer many casualties, something called as “collateral damage” of the urban warfare. Recent examples include Afghanistan and Iraq. In this work, the preparation of soldiers at CIOpGLO is discussed while the possibility of using new approaches based on augmented reality and mixed reality technologies are considered. As a way to enhance training and mission preparation with simulations, this research focus on augmented reality (AR) supported by head-mounted displays (HMDs). HDMs may have many shapes, which include pairs of glasses with lenses that present AR with superposed images, enabling its wearer a total immersion in the simulation. The method used in this work involves a literature review on AR and HMDs, assessment of training needs at the Brazilian Army and an evaluation of emerging technologies from the ICT sector. The technologies to be considered are the HDMs, in this specific case the available programming languages, software and hardware from suppliers of commercial off-the-shelf (COTS) and military off-the-shelf (MOTS). The main contribution of this work is the comparative study of the main solutions for HDM. This study represents an essential step for concept development and for the experimentation to exploit and evaluate the use of simulations. The research presented suggests that the approach is effective and that future work should be on both development of new applications and its evaluation in real training sets in Brazil.