I'm not so familiar with the military but wouldn't it be up to brass like generals or strategic command to decide if the IT infra upgrades are a threat to combat readiness, and prioritize it accordingly?
They can give the CIO budget to do this, but the CIO can't unilaterally decide to do it.
It is up to them, but it's the CIO's job to advocate for his employees and convince them to do it. You hire a CIO to be able to advise you on decisions such as this. The CIO isn't expected to be down in the trenches resetting Active Directory accounts or applying group policies, of course.
They can give the CIO budget to do this, but the CIO can't unilaterally decide to do it.