Dragons in my setting are significantly smaller and less physically powerful than most depictions. The large males reach about 100 kilograms and just over two meters tall. This means that they absolutely cannot carry a full grown man in the air for any appreciable distance.
But despite their more subdued size they are still extremely deadly animals. They are extremely strong and fast on the ground, powerful jaws, a killing claw on each foot and of course fire. They are a highly intelligent animal, akin to a grey parrot or elephant, but they definitely aren’t the intellectual equals of humans and can’t speak.
Humans are able to tame but not domesticate them due to their imprinting instinct as chicks, and that they are easily bribed with food and shiny objects (the value doesn’t matter, they just love shiny due to supernormal stimulus).
The technology level is roughly equivalent to Europe and the Near East in the 13th century. This means the dragons have to deal with longbows, crossbows, and the occasional cannon.
How could people use dragons for warfare that they can’t fly into battle on and that aren’t as intelligent as humans?