The following contains spoilers for Jurassic World: Fallen Kingdom. Consider yourself warned.
Jurassic World: Fallen Kingdom introduces a new type of dinosaur that is specifically designed for a particular purpose. Unfortunately, that purpose is a really bad idea that will never work. The Indoraptor has been genetically engineered with the idea that it can be used by the military as a trained attack animal. The raptor is a vicious killer, that much is true, so what army could possibly stand up to such a ruthless killing machine?
This idea is a holdover from the previous Jurassic World where Vincent D'Onofrio's character had similar machinations, but it was a bad idea then, and it's a bad idea now. While raptors might be technically trainable, this idea simply doesn't hold up scrutiny. If considered for more than five minutes, the entire concept falls apart. Here's why...
You Have To Feed Them
Bringing even one trained velociraptor, never mind several of them, as part of a military campaign, means they are just more mouths to feed. Soldiers aren't traditionally the most well fed in the field with quality food because transporting food in bulk is difficult. MREs are easy to pack. It would be one thing if you just needed to pack a lot of dead meat, but Jurassic World dinosaurs prefer their food alive. If your war is taking place in a location where there is a lot of wild game, you might have a chance, though you'll need to take the time to catch it. Otherwise, your army has to transport an awful lot of live goats to feed your velociraptors or feed the dinos your enemies... which has to be a human rights violation.
They're Not Bulletproof
It's pointed out in Jurassic World: Fallen Kingdom that man has often used animals in war. This is true, of course. Cavalry fighters rode horses. Hannibal crossed the Alps on elephants. But we don't really do that anymore. Why is that? Because if you want to take down a soldier on a horse there's a fairly easy way to do it. Shoot the horse. It's a bigger target. The Indoraptor is fast and violent to be sure, but it's not bulletproof. Send it into a place where an entire army with guns is standing and while it's busy ripping somebody's throat out, everybody else is going to blow it away. We see in the film that the animals are tough, but they're not invincible.