The discrete event systems specification (DEVS) formalism supports the object-oriented (OO) specification of discrete event models in a hierarchical, modular manner. If a system that is to be modeled is domain-specific, the development of models with the use of the DEVS formalism would require domain knowledge about the system as well as to understand DEVS semantics. This paper proposes a collaborative modeling process to compensate for the lack of professional engineers. To compensate, this modeling process utilizes three types of engineers: domain engineer, modeling and simulation (M&S) engineer, and platform engineer. The process consists of four steps: conceptual modeling, model partition, model implementation, and model integration/simulation. The system requirements are used to specify domain models in the conceptual modeling step, and the models are partitioned into two types: discrete event-level model (DEM) and behavioral-level model (BM). The DEM is specified as the DEVS formalism, and the BM is defined as algorithms and equations. Each model is implemented separately, and the implemented models are integrated and simulated flexibly by using a dynamic linking library. The modeling process is then applied to develop a war game simulator. The advantage of this modeling process is that the collaborative work is related to the whole series of steps. This collaboration maximally utilizes the capabilities of the professional engineers by seamlessly separating yet correlating their works.