Half a month later, the army marched to Tongguan 30 miles away and set up camp.

Tongguan is the east gate of Sanqin and the last dangerous pass to enter Chang'an. It is the throat artery connecting Northwest, North China and Central Plains. It is south of the Qinling Mountains, and there is the danger of forbidden ditches and deep valleys; There are Wei and Luo in the north, and the Yellow River hugs the pass; There is a barrier of Huashan Mountain in the west; The eastern mountain peaks are connected, the valley is deep and the cliffs are extremely precipitous, and the danger is extremely steep. As the poet described: "The mountains are strong and the three auxiliaries are closed, and the door is closed and Kyushu is choked."

If Tongguan is breached, Chang'an will basically be in the bag. Therefore, the Sui army attached great importance to it, and sent the loyal and brave general Yin Shishi of Zuo Yiwei, who was loyal to the Great Sui Empire and brave and good at fighting, to lead 15,000 elite soldiers to guard Tongguan.

Yin Shishi, a native of Sui Wuwei, worships Yitong with his father's merits, and moves to the hussar general. Emperor Yang of the Sui Dynasty was too guarded by Zhangye, repelled the attacks of Tuyuhun and Dangxiang tribes, etc., and was deeply feared by Rong Di, and was subdued by one party, and the official was General Zuo Yiwei, who was a famous general of the Sui Dynasty.

Li Shimin now has 20,000 elite soldiers, and after Li Jiancheng added some new soldiers on the road, he now has 10,000 elite soldiers, and the Tang army has a total of only 30,000 soldiers and horses. The Tongguan garrison with dangerous terrain, thick walls and tight defense has 15,000 elite soldiers, and the town guard general is the famous Zuo Yiwei general Yin Shishi, and it is undoubtedly suicide to storm Tongguan. Yin Shishi was a well-known loyal minister of the Sui Dynasty, and it was impossible to persuade him to surrender.

Li Shimin and Li Jiancheng stationed their troops more than 30 miles away from Tongguan, and they were also afraid of a sneak attack by the fierce generals of the Yin Shishi in the middle of the night, because they knew that the Yin Shishi was not the kind of timid and conservative general who would only passively defend the city.

Li Shimin, Li Jiancheng, and the eldest grandson Wuji discussed in the military tent for a few days, but they did not come up with an ideal plan to break the city. But the consensus is that Tongguan must not be stormed.

In the big tent of the Tang army, the eldest grandson Wuji frowned and said: "The grain and grass brought by our army can only last for about a month at most, and the war cannot drag on for too long. If you take the liberty of forcibly attacking the city, you will surely fail miserably! ”

Li Jiancheng nodded, his face worried, "How can I lure the Yin World Master out?" He's a battle-hardened veteran. ”

Li Shimin's face was solemn, staring at the map, looking at it for a while, and said, "It's better for me to lure, I believe that my bait will still make the Yin World Master tempted." ”

The eldest grandson Wuji said worriedly: "His Royal Highness King Qin, you have to be a bait again, isn't it too risky." ”

"I can't bear the burden of the child, I don't take the risk myself. The Yin Shi Master will never leave the city. ”

Li Jiancheng said: "Second brother, you can tell me about the detailed plan. ”

"I decided that from tomorrow onwards, I will only take a hundred cavalry to go around the city of Tongguan every day, reconnoitering the terrain, and I look arrogant and arrogant that I don't think about the Yin World Division and the Sui army defending the city at all, and I look arrogant that the Yin World Division and the Sui Army will not dare to go out of the city to attack. After wandering like this for a few days, I estimate that the famous Yin Shi Shi will definitely blow up his lungs, and as a brave general, he must not want to be laughed at for being timid, and sooner or later he will not be able to help but send troops out of the city to clean me up. ”

Li Shimin added, "In order to dispel the suspicions and concerns of the Yin Shi Division, we don't want to ambush any ambush soldiers nearby, the veteran Yin Shi Shi will definitely be safe and waiting for the quiet reconnaissance and investigation." When he is sure that there are no ambushes around me, and that the army is still more than thirty miles away from me, then he will definitely send troops and even lead them out of the city to arrest me. When the time comes, I will retreat to the mountains to the east, where the mountains are high and dense, the terrain is complicated, and it is not so easy for the Yin World Master to send 2,000 people to capture me, and when I lure the Sui army into the mountains, I will release the wolf smoke signal. At this time, the eldest brother led your five thousand elite cavalry to rescue and entangle the Sui army out of the city. Brother Wuji led an army of 15,000 to Tongguan City to intercept the way back to the city of the Sui army out of the city, and strive to wipe out the Sui army out of the city in one fell swoop. Winning the first battle of Tongguan can hit the morale of the Sui army and boost the morale of our army. Then the camera will act and proceed to the next step. What do you think? ”

The eldest grandson Wuji showed admiration on his face after hearing this, "His Royal Highness King Qin is really daring, this idea is good." However, His Royal Highness King Qin must pay attention to his own safety and not take too many risks. ”

Li Jiancheng was stunned for a moment after hearing this, with a complicated expression on his face, "This is indeed a good idea, but there are some gambling elements." If the Yin World Master only sent more than a thousand people, and he didn't go out to fight himself, then would this not be a surprise, and he would never be able to lure him out of the city in the future. ”

Li Shimin said helplessly: "This is also a helpless thing!" If we keep standing still like this, not only will the morale of the army be unfavorable, but Tongguan will never be breached, and our army will have limited food and grass, and when the grain and grass are exhausted, it will inevitably collapse without a fight. If it is attacked, it will be the next step to lose the troops. Now we can only take one step at a time. ”

In the end, the three decided to act according to Li Shimin's plan. War is inherently uncertain, requiring risk, as well as luck. Li Shimin decided to try his luck this time.