Insects could go in human brains and kill our most important leaders. Fighters would fall as the pilots would get massive headaches and die. Insects would spy on humans and get our most important plans. It probably would be difficult to use submarines and ships as whales would wham on them occasionally. If the armies would on in forests, then the animals would win. If Vietnamese people won by knowing the ground, then think what the apes and jaguars could do.
I guess we would fight back, but we would lose.
well it´s sure that only a coordinate attack could work, and they must be able to sacrifice in order that others Clades or Genera will survive. Foe example all the extant birds could ruin all Air Forces, you know that when they jump into the jumbo motrors that`s a big problem. Some marine animals could ruin navy too. But only for what, ok we make a suicide attak and (let`s says) the rhino conquer the world later?
The one who pointed we are losing the battle against viruses is correct but if we are just insane as thinking to battle against animals let`s use biological weapons, and threat them like a regular plague