The Trojan War is thought to have taken place near the end of the Bronze Age, around or before 1200 B.C. At that time, a Greek civilization we call the Mycenaean was collapsing. The Mycenaens built great palaces and developed a system of writing, and their culture dominated the Greek world for about 300 years before their decline. In the "Iliad," the Greek forces are led by Agamemnon, the king of Mycenae.

The earliest accounts of this war come from Homer, a Greek author who lived around the eighth century B.C. — several centuries after the war supposedly took place. Homer's works were told through oral stories and do not appear to have been written down until even later, likely during the sixth century B.C.

Homer's "Iliad" is set in the 10th year of the Greeks' siege of Troy and tells of a series of events that appear to take place over a few weeks. The story makes clear that the siege had taken its toll on the Greek force sent to recover Helen. The "timbers of our ships have rotted away and the cables are broken 

By this point, the war had essentially become a stalemate, with the Greeks unable to take the city and the Trojans unable to drive the invading force into the sea. We "sons of the Achaians [Greeks] outnumber the Trojans — those who live in the city; but there are companions from other cities in their numbers, wielders of the spear to help them," the "Iliad" says (translation by Eric Robinson). 

A number of key events happen in the poem, including a duel between the Trojan Prince Paris and Menelaos (or Menelaus), the king of Sparta and husband of Helen. The winner is supposed to receive Helen as a prize, ending the war. However, the gods intervene to break up the duel before it is finished, and the war continues. 

Another important duel occurs near the end of the poem between Achilleus (or Achilles) and a great Trojan warrior named Hektor (or Hector). The Trojan knows that he's no match for the Greek warrior and initially runs three laps around Troy, with Achilleus chasing him. Finally, the gods force him to face the Greek warrior, and Hektor is killed. 

The site of Hisarlik, in northwest Turkey, has been identified as the site of the legendary Troy since ancient times. Archaeological research shows that it was inhabited for almost 4,000 years, starting around 3500 B.C. The city was constantly changing, and the settlement was destroyed and rebuilt repeatedly: After one city was destroyed, a new city would be built on top of it, creating a human-made mound called a "tell."

"There is no one single Troy; there are at least 10, lying in layers on top of each other," Gert Jan van Wijngaarden, a researcher at the University of Amsterdam in the Netherlands, wrote in a chapter of the book "Troy: City, Homer and Turkey" (W Books, 2013). 

The Trojan horse, the subterfuge that the Greeks used to enter the city of Troy is shown in this 19th-century engraving.

Source: https://www.livescience.com/38191-ancient-troy.html