For military systems, it is very important that maintenance is performed at the right moment. Too early maintenance leads to high costs and spoiling of system lifetime, while being too late causes failures, leading to reduced reliability and availability. As the operation and operational conditions of military systems are very variable and unpredictable, applying this just-in-time maintenance is challenging. In this presentation, various smart maintenance approaches will be discussed, ranging from accurately monitoring the condition or structural health to predicting failures based on either physical degradation models or (big) data analytics. Several case studies will be shown to demonstrate the concepts.