The background of The Iliad is that the Trojan named Paris kidnaps Helen of Greece and a war breaks out between Greece and Troy. Menelaus, Helen's husband seeks for his brother Agamemnon to help him fight Troy and get Helen back:
Paris visits Menelaus in Sparta and abducts Helen, taking her back to Troy with him, seemingly with her active cooperation. Paris also takes a large part of Menelaus’ fortune. This was a serious breach of the laws of hospitality, which held that guests and hosts owed very specific obligations to each other. In particular, the male guest was obligated to respect the property and wife of his host as he would his own.
The ten-year war between Greece and Troy begins.
In book one, the rage of Achilles is one theme.
As the first word of the Greek text suggests (“Rage! Goddess, sing the rage of Peleus’s son Achilles”), this poem has a lot to do with anger. Honor, glory, and fate are also frequent themes.
Achilles was a brave Greek warrior who captured the beaches of Troy upon his arrival. Achilles should have earned the respect of Agamemnon, the man who considered himself the king of the Greeks, but Agamemnon has no respect for anyone but himself. Agamemnon hates Achilles. In fact, he admits that he hates Achilles most. Nevertheless, Achilles divides the spoils of war with Agamemnon. Agamemnon gets the Trojan girl Chryseis, the daughter of the priest Chryses.
Later, when Chryseis' father prays to the sun god Apollo to get his daughter back, Apollo intervenes and kills many Greeks. Agamemnon is forced to give up his Trojan girl Chryseis. In turn, Agamemnon takes Achilles' girl Briseis. This puts Achilles in a rage. He decides to stop fighting for the Greeks. The Greeks begin suffering many losses due to the fact that Achilles is not fighting with them.
The Greek leaders try to get Agamemnon to give back Briseis to Achilles so Achilles will continue fighting.
In the meantime, Hector kills Achilles' good friend Patroclus. Achilles in enraged. Achilles decides to rejoin the fight. He kills Hector and drags his body. Achilles gets his revenge on Hector.
Later, Priam, the king of Troy, also the father of Hector, tries to ransom his son's body. Priam desires to give Hector a proper burial. Achilles has pity and agrees to give Priam Hector's body:
Achilles is moved to pity the old man and makes him comfortable after agreeing to accept the ransom he offers for Hector’s body. Achilles guarantees the Trojans a suitable amount of time to prepare for and conduct Hector’s funeral.