This is why I use orbital assets for artillery. A frigate in high geosynchronous (sp?) orbit can provide better cover at much less risk if the local anti ship guns were knocked out. Even better park a carrier there and launch fighters while you're at it. You now have an orbital airfield, artillery corps, and command center that are out of reach of most ground forces. But that's me. I tend to try and make the only creatures I send into battle humans. I'm a firm believer in the adage that any job an animal can do, a machine can do better without getting spooked.
Were I to weaponize animals, however, I'd go small. Ticks infested with genetically engineered viruses released into barracks, microbes in the water supply, poisonous plants and countless other little horrors to terrorize an army.
