Alcatel-Lucent, a major telecommunications equipment manufacturer, provides equipment, solutions, and services to customers worldwide. Post-sales support services are a growing business segment for the company, and require significant investment in spare parts. The inventory investment constitutes a considerable portion of the total cost of providing post-sales support services for new customer contracts; it is also an important element in estimating new contract offerings and evaluating and redesigning business processes that affect inventories. Because of Alcatel-Lucent’s two-echelon supply chain structure, inventory sizing for post-sales support services is a complicated task that spreadsheet applications cannot handle adequately. Thus, the company’s repair and exchange services (RES) group needed a fast, user-friendly, and generic software solution with advanced analytic capabilities to support its business tendering and evaluation processes. To meet this requirement, we developed the tactical inventory planning tool, which uses stochastic modeling and optimization algorithms, for this purpose. Although the tool’s primary function is to support the RES business tendering process, it has also been useful in other business analysis because of its generic nature.