Modelling and simulation constitute an increasingly utilized tool within military operations and processes. The applied standard for M&S within the Swedish Armed Forces is the High Level Architecture (HLA). HLA is a framework for simulation development and that provides software and services for distributed execution. Partly due to its great complexity, the framework is unfortunately not fully utilized. One of the services that is particularly complex to use and where support can be necessary is time management and synchronization in HLA. This report presents the research behind, the design and the development of a middlelayer for HLA, the HLAMiddleLayer. The target of developing the layer is to separate heavy HLA logic from simulation development, in order to facilitate utilization of HLA and in addition supply support for more advanced utilization of time management services. Synchronization algorithms implemented in HLA, such as TimeWarp, are developed and presented in detail. Experiments that have been conducted concerning HLA performance are demonstrated and discussed, as well as experiments concerning performance of the implemented synchronization algorithms. The result is presented in a paper that is attached. Finally proposals to further development are discussed.