On the eve of the Xuanwu Gate Rebellion, why did Weichi Gong take a sword to invite Fang and Du Ruhui?

Chigong took the sword and invited two people. First, he sent a signal to them. We can say that this battle is a cross the rubicon and an adventure. Success or failure is at stake. If we fail, we may be wiped out by the enemy in one fell swoop. We should also tell them that at this time, don't think about tipping off the news or beating around the bush. We are already in the same boat. At this time, it is too late to think about anything else, and it is still imminent.

Secondly, I also want to give them a deterrent and let them fall to themselves completely. Because the change of Xuanwu Gate requires not only force, but also civil servants who speak in the court after success to support him. Otherwise, even if the change of Xuanwu Gate was successful, the civil servants in the imperial court would not support Li Shimin, and there was no way to do it. That's enough to give Li Shimin a headache.

In addition, Weichi Gong was asked to protect their safety. Because the situation is very tense at this time, it can be said that it has reached the point of white-hot, and Xuanwu Gate will be changed the next day. Nobody knows what will happen on the way back. Weichi Gong has a weapon in his hand, and unpredictable things can also be carried out at a low level, so that he will not be unarmed and lose his life.

Finally, the change of Xuanwu Gate was successful, and Li Shimin got his wish and killed Prince Li and King Li Yuanji of Qi. But also succeeded in forcing Tang Gaozu to surrender the military power and let Tang Gaozu stand on his own feet as a prince. It can be said that this series of results was expected by Li Shimin. This series of operations of killing one's brother and forcing one's father can be said to be a classic in the battle for imperial power in China, which has been discussed by the world.