He said to let them build a great wooden horse.
The statement "He said to let them build a great wooden horse" alludes to the story of the Trojan Horse from Greek mythology. In this tale, the Greeks, after a long and unsuccessful siege of the city of Troy, devised a plan to trick the Trojans. They built a large wooden horse and hid a group of soldiers inside.
The Greeks then pretended to sail away, leaving the horse behind. A Greek soldier, Sinon, was left behind to convince the Trojans that the horse was an offering to the gods and that it was meant to be brought inside the city walls. Despite warnings from some, such as Cassandra and Laocoön, the Trojans, curious and perhaps believing they had won the war, brought the horse inside their city.
During the night, the Greek soldiers emerged from the horse, opened the city gates, and allowed the rest of the Greek army to enter, leading to the fall of Troy.