Dating back to the Sumerian Empire of Mesopotamia (modern Iraq), the epic poem known as The Epic of Gilgamesh contains what is believed to be the first formal declaration of war. Among the earliest works of literature, this poem describes the exploits of Gilgamesh, the king of Uruk in Mesopotamia in approximately 2500 BC. Scholars believe the poem was originally composed in 1800–1700 BC (nearly 1,000 years before Homer is thought to have written The Iliad and The Odyssey) and later recorded on clay tablets some time between 1300 and 1000 BC.

In modern times, declarations of war are enmeshed with international law emanating from the Hague Conventions of 1899 and 1907. But, throughout history, wars have been fought without such declarations. This is also true in our time as since World War II, for example, the United States has not fought a “declared war” despite engaging in several armed conflicts, including Korea, Vietnam, Iraq and Afghanistan. In fact, the United States has made only five formal declarations of war in its history: the War of 1812, the Mexican-American War, the Spanish-American War and World Wars I and II.