A Soldier in AntWar.io is a type of ant that usually appears late - mid - game whose primary purpose is to fight other Ants. Soldiers are slower, so it is advised not to use them to gather resources. They cost one Super Food and two Meat, so as soon as you kill a Spider, it is best to make Soldiers.
Soldiers should primarily be used for fighting. They are slow, meaning they can't gather resources as fast as a Nanitic or Worker. However, they do have more health and also deal more damage than them, allowing them to help kill a Centipede. While two Soldiers are stronger than a Major, it is still best to build Majors once you have a lot of Super Food. This should only be done during late game though, where Super Food is abundant. If you would run out of Super Food with Majors then it would have actually been better to build Soldiers.
Soldiers deal 22 damage, which makes them almost three times as much better warriors than Workers. Soldiers also have 130 health. Combined with their damage, this means that a single Soldier can pick off three Workers. However, it won't be able to kill the Workers if the Workers are all in a single group. For that it needs multiple soldiers to soak up damage. Soldiers only have 5 speed, so a Worker is exactly a fifth faster. This can add up.
Soldiers do not spawn naturally; they can only be created via the Egg Selection menu.