Final answer:
Enemy forces are those who have declared war or on whom war has been declared. They include states or non-state actors involved in armed conflict.
Step-by-step explanation:
Enemy forces refer to those who have declared war or on whom war has been declared. In the context of warfare, enemy forces typically include states or non-state actors that are engaged in armed conflict. For example, during World War II, the enemies of the Allied forces were Germany, Italy, and Japan. In more recent times, the notion of enemy forces has expanded to include non-governmental organizations involved in acts of terrorism, such as al-Qaeda and ISIS.