Consider Ancient Rome. If some proportion of soldiers in Caesar's military had the ability to shoot small jets of fire out of their hands for a maximum duration of 1 second, and perhaps a total limit of 3-4 times (or perhaps the only limit is physical exhaustion), do you think that forming battle lines would become obsolete?

A major part of maintaining a battle line is psychology. The most deaths in warfare occur when the soldiers panic and flee, breaking the line. I think having fire shot at you would be pretty panic inducing.

Could this lead towards trench warfare?

Possible counters include shields wrapped in leather and soaked in vinegar, and also asbestos. Short article about asbestos

  • 1
    $\begingroup$ What proportion of soldiers are we talking here? One per legion? Per century? A handful of specialists, like an artillery battery? Every third guy standing in line? $\endgroup$
    – Cadence
    Nov 1, 2019 at 17:23
  • $\begingroup$ If magic to toss fire at the enemy, then presumably magic for the enemy to catch it and toss it back. Or fling water back. $\endgroup$
    – puppetsock
    Nov 1, 2019 at 17:24
  • 1
    $\begingroup$ Is this only Caesar's army, or do all armies have it? And is this natural to humankind, or is this a device shooting the fire? $\endgroup$
    – Cort Ammon
    Nov 1, 2019 at 17:26
  • 1
    $\begingroup$ how far they are able to project their flames could matter as well, pike weapons could reach lengths of 17 feet and could be an easy solution already available $\endgroup$
    – BKlassen
    Nov 1, 2019 at 17:28
  • 3
    $\begingroup$ What range would these people have? And how does the fire behave? A stream acting like a short-duration burning liquid/gas can be handled differently than what amounts to a firestream capable of penetrating an inch of steel. Heat capacity is also important to know what it does to its targets and know its lethality $\endgroup$
    – Demigan
    Nov 1, 2019 at 17:30

3 Answers 3


In short: no.

Having an ability to shoot fire just means the battle line can advance 3 or 4 times with fire over the course of the battle. This could be used to try to break lines, or protect friendlies in the heat of battle, but probably wouldn't be the main source of inflicting damage.

When the soldiers ran out of their 4 charges of fire, the fight would continue with traditional means.

The point of a battle line is to mitigate the ability of the enemy getting behind you, and to maximize the surface area in contact with the enemy. Soldiers can't stand closer together than touching, and each basically carry one weapon. By keeping them close, every enemy is within reach of approximately 3 soldiers, 3 swords, and potentially 2 spears from the soldiers behind reaching through the gaps. Soldiers also work to shield each other from damage, meaning each soldier is protected by 3 shields.

When a line breaks, soldiers lose the force multiplier of their fellow soldiers being near, and now have to take on one or more enemies on their own.

  • $\begingroup$ And what if fire charges were only limited by physical exhaustion, like traditional fighting? $\endgroup$
    – Pixel S
    Nov 1, 2019 at 17:42
  • $\begingroup$ If 4 charges exhausts the soldier, then they would likely use less fire, not more, saving their strength for opportune moments. If it's a more "same energy as a sword swing" situation, then it'd likely be a mix based on the situation, but still a mix of traditional and fire combat. $\endgroup$
    – Stephan
    Nov 1, 2019 at 17:45

You indicate that properly prepared shields can be used to ward off the fire attack without being too badly damaged. However, shields are only really useful in one direction at a time - if someone can come at you from an angle and get around your shield, it's worthless. On the other hand, if you form a battle line, you can make it more difficult to outflank your line of shields, and if you have a second rank of troops, they can cover areas the first can't (the sides, and top if someone is throwing missiles at you). This is the principle of the famous testudo formation, which the Romans were experts at using.

As a legionary, your odds of surviving any missile attack - arrows, slings, magical bolts of fire, whatever - are materially improved by sticking to a tight formation where you can present multiple shields in an overlapping defense. And once you're in a tight defensive cluster, it takes a lot more effort and focus to leave it - after all, running off on your own is just going to make you a target.

  • $\begingroup$ +1 for pointing out that the importance of battle lines are actually improved and not just still viable. $\endgroup$
    – Nosajimiki
    Nov 1, 2019 at 18:51

We can look at when battle lines became obsolete: WWI.

Before WWI we had muskets, capable of defeating most types of armor and fired in volleys. They still used battle lines despite a single volley potentially taking out dozens of soldiers, and these people could fire many more than 4 per day. Admittedly they couldnt do it in a second long burst, but it would have similar consequences on the long-term.

As an aside, it is unlikely that most of these people would hit the target effectively. Even during the musket days the "fire above the enemy and look busy" model of fighting was what happened. It even happened that after a fight muskets could be found that had been loaded multiple times but never fired simply because in the heat of battle that person wasnt aware his gun wasnt firing or he just didnt want to fire. A more likely thing that would happen is that these streams of fire are used in front of the enemy or just over their heads instead of directly at them.

Ignoring the "people dont want to kill people" thing it was the machine gun that ended the battle-line era and started the trench warfare. Even with a second of fire and murderous intent of the user it is unlikely to be lethal enough to stop battle-lines from being used. They would even be likely to field non-fire troops up front to identify the fire-wielders up front and fire a quick volley at them. If low amounts of the population have the skill then they would be used as a shock weapon against cavalry or to disrupt a formation somewhat just before a charge against a high-value target (regardless of it being the attacker or defender).

  • $\begingroup$ If you consider the end of formations to be trench warfare, it may be more accurate to say they became obsolete during the American Civil war. The civil war saw the first wide scale use of gatling guns, bolt action rifles, and trench combat. The North lost many early battles despite superior numbers and firepower because they did not know to dig in. By the end of the war, digging in or setting up temporary stockades became the norm. $\endgroup$
    – Nosajimiki
    Nov 1, 2019 at 19:06
  • $\begingroup$ Another interpretation is that trench warfare is just another form of fighting in formation, and that formations did not truly become obsolete until WWII when mobility based warfare took center stage. $\endgroup$
    – Nosajimiki
    Nov 1, 2019 at 19:10
  • $\begingroup$ @Nosajimiki I used WWI because battle lines were still used in WWI, and subsequently punished by the machinegun technology causing it to fully cease. I didnt know trench warfare was used in the American Civil war and battle lines stopped being used there then as well. $\endgroup$
    – Demigan
    Nov 1, 2019 at 19:35
  • $\begingroup$ @Nosajimiki digging a trench and holding a trench is a very viable tactic for the infantry even today. $\endgroup$
    – Alexander
    Nov 1, 2019 at 19:45
  • 1
    $\begingroup$ @Alexander Agreed, but it is no longer used in the form of battle lines. When modern armies entrench it is typically to hold small places of tactical significance. You might entrench a squad or maybe a platoon, but you wouldn't entrench a whole army in a single tightly packed formation. $\endgroup$
    – Nosajimiki
    Nov 1, 2019 at 20:03

Not the answer you're looking for? Browse other questions tagged .