This paper introduces user intervention to control simulation states during the execution of a simulation for military engagements. In an engagement simulation, it covers both a discrete event system and a continuous state system. Thus a system for the engagement simulation can have numerous simulation states, because there are lots of factors to decide states of an engagement that are derived during an execution of the simulation (e. g. detection probability, moving speed, moving path, and so on). It means both a result and progression of simulations are important outputs. Configuration of an engagement simulation scenario and expectation of simulation states, though, is hindered by the number of generate-able states. In order to solve the obstacle, the engagement simulation system should be controllable by user intervention during a simulation execution. This paper is to define objects of user intervention, and to design control processes of defined objects.