## 4 Discussion  
This study discusses the prototype resilience model that has been developed in order to discover whether the NATO resilience capacity can be measured in a dynamic way. The model was developed using a system dynamics approach to be able to reflect the interactions among related variables and  
Figure 8: Sample output graph of risk assessment functions for baseline (normal) and extraordinary scenarios.  
Figure 9: Sample output graph of resilience main domains for baseline (normal) and extraordinary scenarios.  
parameters to the maximum extent. The rationale behind choosing this approach is to converge the model interrelations and interactions to the real-world behaviours in the resilience domain.  
The implemented model running both baseline (without any shock) and extraordinary scenarios (with strategic shocks) clearly demonstrates its capacity to represent quantitatively the resilience related factors of a country in a complex operational environment in a dynamic way.  
Moreover, the outputs of the prototype model substantially comply with the resilience concept existing in the literature and NATO applications.  
One of the main strengths of the prototype model is its almost infinite capacity to create various scenarios and make a lot of what-if analysis limited only by the current number of endogenous parameters of the model. It allows studying the second and third order effects of events introduced in the scenarios as the critical activity for understanding the resilience concept and related risk to the military operations.  
The user interfaces (input and output dashboards) of the model help decision makers modify the values of selected endogenous parameters, see and compare the time-based values of the resilience factors, and doing so to evaluate risk related to the area of NATO operation.  
The prototype model can provide foresights about situational behaviour changes in the NATO resilience system over time. The outputs of the model can also be used as add-in alternatives together with other extant descriptive results.  
Users' validation workshops revealed that a descriptive methodology that transforms scenario data into the model input parameters values is the most critical aspect of the model's successful employment. Without explicit formulation of the transformation mechanisms, the qualitative output of the resilience model may be misleading.  
The aforementioned model has space for further development, as the users are identified through the model validation series of workshops. Adding more countries to the model and bringing the aggregation mechanism to output values of both resilience capacity and risk functions over a single area of NATO operation is the main project way ahead. Extension of the current set of existing shocks and bringing more user-defined parameters can be another objective for the development of the NATO Resilience expert system.  
Conceptualization, J.H. and H.O.; methodology, J.H., P.S., and J.D.; software, G.O. and H.O.; validation, J.H., H.O., and G.O.; formal analysis, J.H. and H.O.; investigation, H.O. and G.O.; writing--G.O. and H.O.; original draft preparation, P.S. and J.D.; writing--review and editing, W.B., J.H., and P.S.; visualization, G.O. and H.O.; supervision, P.S. and J.H.; project administration, J.H.; funding acquisition, J.H. All authors have read and agreed to the published version of the manuscript.  
This research project was funded by NATO HQ SACT.  
The authors declare no conflict of interest.