[Gud]

Any decent military will be using multiple forms of communication systems.

I was a communications specialist for the Swedish Armed forces 10+ years ago, including a tour in Afghanistan and a tour in Kosovo.

We used radio links for internet that I can tell you, were more adversarial than friendly.

The Swedish military is highly capable when it comes to network communications. A small nation will have to think differently.

You could potentially use an instant messaging system in control by someone else, if you are willing and capable of sharing encryption keys with whomever you are going to communicate with beforehand.