Depending on what kind of a unit he’s in, he could try generating a discussion about what core tasks for the unit aren’t utilized/practiced during their deployment.  In essesnce, if the US declared war on a near-peer nation-state tomorrow, what tasks would your unit be expected to execute that you are not prepared to do?

Having witnessed this discussion both in MI and Cyber, it is hard to separate what you need to do for current operations from what you need to be capable of doing in the future.  This might be a good primer for looking at past failures along these lines.