HF is the only option for regional communications. If you’re an HF operator, you know the past couple of years have been rough on many of the bands due to the solar minimum. But the good news is that the solar cycle is heating back up, leading to a resurgence in HF capability at low power- QRP- and a shallower learning curve to those new to the craft.
That said, the US Army has had voices in the background trying to keep HF relevant even as satellite-based communications have taken the forefront as they’re simpler on the operator’s end and generally more reliable. But in a near-peer conflict like one with say, China, TACSAT is no longer an option, nor is conventional means of electronic encryption. HF is the answer.
This article from Military and Aerospace Electronics, and sent to me by reader GreenArc, published back in 2002, covers in detail the options and advantages in a military context to why HF is critically important:
Still, the HF bands offer profound advantages to those who can deal effectively with the problematic nature of this medium. To begin with, HF communications have the potential to move voice and data communications around the world by bouncing signals off the ionosphere, and at a fraction of the cost of heavily burdened satellite communications frequencies. In addition, HF transmissions often can circumvent geographic barriers to line-of-sight communications such as mountains or buildings by skipping signals off the ionosphere at steep trajectories. The benefits of HF radio communications are too good to ignore.