#fire attack

Not very. Fire attacks are difficult to organize and execute. They're better for smoking out targets from flammable fortifications than creating a ring of fire. You can burn down a forest to burn out guerillas or force enemies to flee, but you also deprive yourself of valuable resources and deny yourself the area, and fire is an indiscriminate attacker that can easily burn your own men. This means that you have to be conscious of the wind and the presence of flammable materials that can spread the fire in directions you do not want it to go.

This is a benefit of dragons, you can use fire attacks very easily, avoiding the need to assemble and transport materials and ensure the fire gets lit and gets large enough to be useful. Since dragons fly, you can start a fire and fly off, significantly reducing risk of friendly forces being caught in the blaze.

Sharpened stakes are easier area denial weapons to defend critical chokepoints. Even without mass production techniques, you can make stakes anywhere trees are present.

Thanks for the question, Flag.