> "Famously Margaret Thatcher claimed that there was no way for her to have ordered the submarine attack on the General Belgrano during the Falklands War as she could not talk to a submarine in the ocean depths off of the tip of South America. I later learned from a Telecoms expert that they had a system of sending long waves through the Earth's crust to reach any point on earth designed specifically to reach submarines in distant waters."
The Military have had ground radio since the time of Tesla and Marconi. They can transmit signals to submarines.
However, the Military don't keep 'Operational Staff' 'in-the-loop' about the State or Capabilities of their Communication Facilities.
"Operational Staff" includes the range from the Prime Minister down to Sailors on the Submarines.
The actual Radio Bandwidth might be low, but messages can be transmitted.
If you go onto most Submarines, you will find that the Communications Room is "Top Secret" and they don't even want anyone knowing what type of equipment is even inside the room. Not even the Submarine Captain is usually given Military Hierarchy over the Communications Officer.
So that is a small insight into how the system works.
TTE is a related Communication system, that you can read about here :