During the recent years the development within the area tactical laser weapons has progressed relatively rapidly. Average laser power in the range of 100 kilowatt has been achieved using diode-pumped solid state lasers. Tactical laser weapons are e.g. discussed as a future alternative within the air defence to defeat threats from artillery, mortars and rockets for protection of camps. The advantages of a tactical laser weapon include speed of light engagement, possibilities to defeat several targets within a short time period, reduced collateral damage and adjustable target effects. By reducing the weight, volume and the technical complexity vehicle mounted tactical laser weapons are presently considered for operational use. In order to evaluate performance and capabilities of tactical laser weapon systems simulations based on optical modelling can be employed. A tactical laser weapon contain several sub-systems such as the high power laser, transmit telescope, mechanical gimbal, target tracking system and adaptive optics. All these parts need to be incorporated in system modelling. Performance limiting perturbations include mechanical vibrations and atmospheric effects (scattering, absorption, turbulence, thermal blooming). Another important issue is the target interaction. The objective with this work was to provide a preliminary analysis of phenomena and technical requirements governing the modelling of a tactical laser weapon. The report contains an overview of technology, phenomena and definition of critical parameters. Different components and sub-systems have been analysed and the most important functions and properties are summarised. A simplified model that can be used to estimate performance has been described. For more comprehensive simulations a numerical model needs to be developed based on modules that successively may be merged into a system model. A scheme for development of a system model capable of simulating the performance of a tactical laser weapon has been presented.