For as long as there have been armies, war has carried a brake built into it: it costs human lives to wage. Soldiers die, families grieve, nations count the price. That cost, terrible as it is, has always been one of the few forces that made leaders hesitate before they began.

Autonomous weapons remove that brake.

The battlefield is becoming algorithmic. Drones that select their own targets, ground units that patrol and engage with minimal human input, systems that detect, decide and strike faster than any person could intervene. This is not a distant scenario. The components exist, the doctrine is being written, and every major power is moving in the same direction at once, because no one dares be the one who moves second.

The technical questions are real, but they are not the deepest ones. The deepest question is moral, simple to state and very hard to answer: should a machine ever be permitted to decide, on its own, to end a human life? Once that decision is delegated to a system, accountability begins to dissolve. If an autonomous weapon kills the wrong people, who is responsible – the commander who deployed it, the engineer who trained it, the model that made the call in a millisecond no human could review? We do not have a good answer, and we are building the weapons anyway.

There is a second danger, quieter than the first. When war no longer costs your own soldiers, it becomes easier to start. Remove the body bags coming home, and you remove one of the last political restraints on using force. A war that is cheap in human terms for the side with the machines is a war more likely to be fought. Efficiency, on a battlefield, is not obviously a virtue.

I am not naive enough to think this can be uninvented, or that any single nation will disarm alone. But the history of the weapons that horrified us – chemical, biological, nuclear – is also a history of hard-won lines that most of the world agreed not to cross. The line for autonomous lethal force is being drawn right now, while it is still abstract. That is exactly when such lines get drawn, or lost.

The machines will be able to fight our wars for us. The question we have to answer first is whether a decision this grave should ever be made by something that cannot be held to account.