Final answer:
Poseidon's grudge against the Trojans fueled his desire for revenge and influenced his actions during the war.
Step-by-step explanation:
Poseidon's grudge against the Trojans affected his behavior during the war in several ways. One example is the story of Laocoon, a Trojan priest of Poseidon who warned the Trojans about the Greeks bearing gifts. Poseidon, upset by Laocoon's warning, sent two sea serpents to kill him and his two sons.
This grudge also led to Poseidon creating a sea-monster named Cetus to devastate a kingdom because Queen Cassiopeia had compared her beauty to that of the Nereids, Poseidon's daughters.
This shows that Poseidon's grudge against the Trojans fueled his desire for revenge and influenced his actions in the war.