system
Given the following post, respond as if you're commenting on Reddit:
human
[Dune] How did warfare evolve into melee combat?

Before someone answer Shield, I thought Shield would only remove projectile-based weaponry from the equation. The following things should be safe from Shield: Chemical warfare, biological, thermonuclear, and probably many others. And apparently people still send conventional foot soldiers with swords out in the battlefield, and the opposing side greets it with the same soldiers and swords. Why don't people shower each other in infinite bacteria, viruses, chemicals and nukes? If laser guns meet Shields with a nuclear explosion, why aren't there suicide bombers? Is there an Arrakis Convention regulating warfare?
gpt
Nuclear attacks would bring the attention of all the great houses, which would glass the offender’s world. 

Since interstellar travel is totally dependent on the Spacing Guild, they would need to get biological or chemical weapons through Guild security measures. The guild relies heavily on spice and its prescience capabilities and refuses to be party to such tactics.

Slug throwers are still in use but will only work against non-shielded opponents. The great houses can afford personal shields for their armies, meaning that only hand-to-hand combat.