In this master thesis project, we use mathematical inventory modeling to give Royal Philips strategic insights in their Japanese service network. The implemented model, based on the model from Kranenburg and Van Houtum (2009), considers multiple central warehouses and local warehouses and allows for lateral transshipments and emergency shipments. The model consists of an evaluation based on the Erlang loss model and a Greedy heuristic that optimizes stocking decisions while satisfying Material Availability targets. The model is used to learn more about the sensitivity between service levels and the corresponding service network costs. Additionally, it gives insight in the effects of optimizing with an aggregate waiting time target, studies the dependency on one of the network’s Regional Distribution Centers and shows the effects of decreasing replenishment leadtimes against higher transport tariffs.