## 1 Introduction  
The change in the modern battlefields to local and asymmetric warfare has forced the armed forces of major nations to find solutions for expanding their abilities in responding to these changes [1]. Since their existing capabilities are limited with respect to coping with current battlefields involving new and potential threats, the acquisition and deployment of new weapon systems are important to prepare for expected conflicts [2]. This means that traditional approaches for the design of weapons need to be modified to prepare for unprecedented aspects of warfare. The solutions include the enhancement of existing weapon platforms or a revision of their designs [3]. Designers need a comprehensive understanding of the potential battlefield environments for weapon system design; based on their understanding, they need to derive technical factors that enable functional requirements,while considering the interactions among these factors to design new weapons [4]. Moreover, both the design and evaluation of weapons are important, and technical approaches are needed to support both aspects. One of the practical alternatives is to employ modeling and simulation (M&S) techniques, which can be utilized as tools to support the design of complex systems [5], and which are also applied to the development of weapon systems. It provides opportunities to confirm the strengths and weaknesses of weapon systems during their development without actual tests. In particular, the techniques can be used to determine their ability to perform specific missions or to check shortfalls when encountering specific threats [6]. Currently, M&S techniques are widely used for acquisition, training, analysis, test, and evaluation missions [7]; the armed forces of major nations utilize M&S techniques to reduce the development cycle of weapon systems [8]. The importance of M&S techniques will increase as the complexity of weapon systems grows [5].  
However, the application of M&S techniques to the weapon development process involves potential difficulties derived from similar studies. First, there is no simulation model that provides solutions for all problems of any specific field; hence, designers should design certain models for the specific purposes [6]. Second, although a model of the same type is designed, its forms can be diverse according to the intention of designers; moreover, it is difficult and time consuming to perform modeling that satisfies every demand [9; 10]. Third, the increase in the number of requirements can cause an increase in the number and relevance of constituents and increase the complexity of modeling [4].  
This paper aims to define efforts to handle these issues, and includes designing a reusable modeling method, intelligent modeling process, and simulation to test the model. Consequently, our proposed method has the following three benefits: (1) It provides a generalized structure and its parts for each weapon system to design the constituent modules, (2) it offers an automated modeling process that covers all design factors through an intelligent method such as case-based reasoning (CBR), and (3) it furnishes a simulation to test the generated models for the expected operation environments.  
The organization of the paper is as follows: Section 2 explains the related techniques and studies for reusable modeling and intelligent modeling for simulation. Section 3 describes in detail the intelligent method for modeling and simulation (IM4 MnS) to support the development of weapon systems. Section 4 discusses a case study on weapon system modeling using IM4 MnS based on the process explained in Section 3. Section 5 describes the experimental results showing the survivability of the designed model, and Section 6 concludes the study by summarizing the results, contributions, and limitations.