Imagine a laser capable of melting through a 1 inch steel plate in a second. Pretty impressive, no? Good, now make it 100,000 times more powerful. That's gamma rays.
Recent tremendous advances in linear accelerator miniaturization (LAM) have completely revolutionized our capability to produce gamma* radiation cheaply and abundantly.
Photon energy levels previously only attainable in distant cosmic object like magnetars, black hole accretion disks or as bremsstrahlung radiation in the most powerful cyclotrons of the previous decade (2010-2020) are now attainable in a vehicle-portable tabletop sized device.
Due to the rapidly deteriorating security situation in the world, it is perhaps not surprising that the immediate application of the LAM technology is in the military area. With the involvement of DARPA and a number of secretive startups, the US has developed a lead in the field, and the most public of the startups has unveiled a prototype to US CENTCOM, where they estimate that a 1-meter diameter fixed-sentry (journalists quipped that it was shaped a bit like a Dalek from Dr. Who, minus the wheels) can be built for $50,000 and, with an appropriate power source, is capable of near-continuous (90-95% uptime) devastating fire in the MeV range ("fluorescence" is the current euphemism) with virtually no maintenance for up to 1 year unless physically damaged by enemy fire. The latest version also boasts impressive angular velocity and target acquisition and engagement speed is so fast that is it said that a human cannot actually see it move.
While the US pioneered the technology, US adversaries are working overtime to replicate the technology, and the most advanced will probably succeed in doing so in the next few months/years. Already unreliable, overheating prone, lower-power versions have popped up in the arsenals of non-state actors in the never ending conflicts in West Asia.
What would the main effect of such gamma-ray sentries be on the battlefields of the near-future? Can maneuver warfare persist under these constraints?
*Gamma rays are extremely high energy, typically thousands to millions of electron-volts per photon, compared with 1.5-3 electron-volts per photon for visible light. So like light, except a million times more powerful, heh, heh.