The Feast at Hong Gate (Traditional Chinese: 鴻門宴, Simplified Chinese: 鴻門宴, pinyin: Hóngményàn) was a historical event (206 BC or 205 BC -- it happened around the new year) later often memorialized in Chinese history, novels, and drama, including in Beijing opera.
The feast came about due to the jealousy and resentment of Xiang Yu (項羽/項羽) towards Liu Bang (劉邦/劉邦), who had conquered the heartland of Qin Dynasty and caused its destruction; Xiang had considered the destruction of Qin to be the prize reserved only for him. Xiang was also angry that Liu, assuming that he would be made the Prince of Qin, appeared to be about to make the last ruler of Qin, Ying Ying, his prime minister in governing Qin. Outnumbering Liu by about three-to-one and considering himself to be the superior general, and further instigated by his advisor Fan Zeng (范增), Xiang was set to attack Liu and annihilate Liu's army.
Xiang Yu's uncle Xiang Bo (項伯/項伯), a general in his army, found out about this plan. Being a good friend of Liu's strategist Zhang Liang (張良), he secretly rode to Liu's camp at night and told Zhang what was happening, trying to persuade Zhang to return to Xiang's camp with him and avoid the slaughter. Zhang, arguing that he had an obligation to Liu, refused, and further arranged a meeting between Xiang Bo and Liu. Liu flattered Xiang Bo and promised to be subservient to Xiang Yu and to pay respect to Xiang Yu the next morning, and Xiang Bo believed him. Returning to Xiang Yu's camp, Xiang Bo persuaded Xiang Yu that it was inappropriate and ungrateful to destroy Liu and his army. Instead, Xiang Yu began to set up a feast to entertain Liu the next day.
The next morning, Liu rode to Xiang Yu's camp with a small contingent of guards to pay respect to Xiang. He apologized to Xiang for robbing him of his glory but at the same time extolling Xiang's valor in battle. Xiang responded with sarcastic words but then started the feast. During the feast, Xiang considered killing Liu, and Fan gave him multiple signals to do so, but Xiang could not make the decision to do so. Fan then summoned Xiang's cousin Xiang Zhuang (項莊), giving him instructions to do a sword dance as part of the entertainment and to stab Liu to death during the dance. With Fan's instructions, Xiang Zhuang indeed offered to do a sword dance, and with Xiang Yu's approval, started dancing. Xiang Bo, who had by this point been convinced that killing Liu was wrong, saw through the plan and started dancing as well and blocking Xiang Zhuang from being able to stab Liu.
When Zhang, who was also at the feast, saw what danger Liu was in, he went outside and summoned Liu's chief guard and brother-in-law Fan Ceng (樊噌), who advanced in full armor into the feast tent despite not having been invited, interrupting the sword dance. While offended, Xiang was also impressed by Fan Ceng's bravado, and gave him an urn of wine and a pork shoulder -- which Fan proceeded to eat, using his shield as a plate. Xiang was further impressed. Fan then gave a lengthy speech about Liu's accomplishments and how it would be unjust for Xiang to kill him, but also implicitly confirming that Liu would not challenge Xiang's authority. Xiang did not respond but invited Fan Ceng to join the table. Fan Ceng sat next to Zhang, and they planned an escape. Soon, when Liu was going to the latrine, Fan accompanied him, and they took a single horse (to avoid attention) for Liu to ride on to escape, with only Fan and several other guards -- Xiahou Ying (夏侯嬰), Jin Jiang (靳疆), and Ji Xin (紀信) accompanying him on foot.
Zhang Liang remained at the feast. After a sufficient time period, in which he thought was enough for Liu to escape, he bowed to Xiang and apolologized on Liu's behalf for leaving, giving as the rationale that Liu had become drunk and unable to continue at the feast. He offered, as gifts, a precious jade tablet for Xiang and a pair of jade measuring cups for Fan Zeng. Xiang accepted his gift, but Fan, in disgust, threw the cups on the ground and cut them to pieces with his sword, predicting that now that Xiang had failed to kill Liu when he could, Liu would eventually lead to Xiang's downfall -- words that would turn out to be prophetic.
In Chinese idiomatic usage, "the Feast at Hong Gate" has often been used to refer to a trap or a situation ostensibly joyous but in fact treacherous. Another idiom that relates to the event is "Xiang Zhuang's sword dance is aimed at the Duke of Pei" (Xiang Zhuang wujian, yi zai Pei Gong; "Duke of Pei" being a title that Liu had at the time), meaning that a person's acts were intended to be a veiled attack on another person.