The military intervention on Latin American governments is such an important issue that so many scholars on Latin American affairs have given at least thought of writing or have writtern on the subject matters. In their writing one can draw a major theme or patterns of behavior of military insitution as the distinguished writers such as Professors Edwin Lieuwen and John Johnson have done. Professor Lieuwen describes the military institution as an proponent of maintaining of status quo as well as an obstacle for change of the existing political and economic institution. Though somwhat different but similar line of thinking is also expressed by Professor Johnson who proposed an important hypothesis that in the increase of the middle sector by the process of economic development of Latin American countries, military becomes likely professionalized and will not participate in politial intervention. In other words, the military will become a supporter of the middle sector`s policies of industrialization, nationalism, enhancement of educational program, and urbanization. One should point out that middle sector which professor Johnson mentioned is, by definition, a rather ambiguous and confusing term. On the other hand, Professor Samuel Finer hypothesized that the propensity for military intervention is likely to decrease with increased social mobilization. Thus, this writer attempts to prove that the above proposed several hypotheses may have a minimal and limited validity but largely distorted. To prove this writer`s thesis that role of Latin American military varies according to the stages of economic development of the respective countries, the type of military intervention, the motivations and role of military interventions in the light of civil-military relations, and of middle class military and social change are analyzed and assessed in terms of their political participation. The conclusion is as follows: First, where less than 10% of the middle class is existed, unlike the thesis of Professor Lieuwen, the military institution somewhat identifies with oligarchy, but plays a vital role of reformer. Second, where the, transitional society characterized with less than 19% but above 10% of the middle class existed, the military plays role of mediator or participant in political affairs. Third, in mass society, the Latin American military is, unlike the theses of Professor Johnson and Finer, certainly played a vital political role so as to prevent mass participation in politics as we have seen in Argentina, Brazil, and Chile in recent years. As Jose Nun rightly pointed out in his book entitled, "Obstacle Change in Latin America," the Latin American middle class is most greatly effected sector by variety of unstable government decisions; thus, it is the middle class that encourage rather than discourage the military to take part in politics. Indeed, the middle class is unstable factor in Latin American politics without even having their own value system. Therefore, one can easily foresee that Latin American military move their direction right and left depending upon their stage of economic development as well as upon the degree of mass participation in politics. One can-also draw a pattern of military intervention as follows: 1. in the past the Latin American military coup detate were promoted by high ranking officer or a group of officers, but the present coup tends to be ocurred in coorporation with three branches of military institution due to the increased complexity of political activities and processes; 2. traditionally, military intervention was a transitory nature until the reestablishment of social order by civilian, but new military has not only any intention of allowing participation of civilian except a few technocrats as cabinet members but also does not set any time limit of their rein.