At the beginning of 192 A.D., Gongsun Zan(公孙瓒) was defeated by Yuan Shao (袁绍)at Jieqiao (界桥).
After returning to Youzhou (幽州), he reorganised his troops and allied with Yuan Shu (袁术) in the south to prepare for another southward battle with Yuan Shao.
Soon Gongsun Zan ordered Liu Bei(刘备) to garrison Gaotang(高唐) and Shan Jing(单经) to garrison Pingyuan(平原), while at the same time uniting with Tao Qian(陶谦) of Xuzhou(徐州) and Yuan Shu of Nanyang (南阳)to march out together ,trying to pincer attack Yuan Shao and Cao Cao's (曹操)clique, from the three directions of the east ,south and north.
Yuan Shao and Cao Cao discussed their countermeasures and attacked separately, defeating the allied forces of Yuan Shu, Gongsun Zan, and Tao Qian, while Yuan Shu retreated to Shouchun(寿春).
At the end of the same year, Gongsun Zan once again marched to Longcou(龙凑), but was defeated by Yuan Shao again, which forced Gongsun Zan to retreat to Youzhou. After several fierce battles in a short period of time, both Yuan Shao and Gongsun Zan were exhausted, suffered heavy casualties, and ran out of food.
At the beginning of 193 A.D., Zhao Qi(赵岐),came from Chang'an(长安) by order of Emperor Xian of Han(汉献帝189AD-220AD)to urge for peace, then Yuan Shao and Gongsun Zan both declared a truce.
Because Yuan Shao has always set Gongsun Zan as his top enemy, the focus of Jizhou's(冀州) defence has always been in the north, now the northern part of Jizhou has managed to have a temporary truce, but before Yuan Shao can take a breather, the southern part of Jizhou is in a big mess again.
At that time, the border area between Jizhou and Yanzhou(兖州), together with the area around Bingzhou(并州), was an active area for peasant rising insurgents.
In 193 A.D., a unit of the Black Mountain Army(a rebellion army), with several tens of thousands of men led by the leader Yu Du(于毒), took advantage of the fact that Yuan Shao's main forces were in the northern part of Jizhou, and the internal void, and surprisingly captured Yecheng(邺城), the capital of Jizhou.
At that time, the families of Yuan Shao and his subordinates were in Yecheng, and when they heard the news, some of them were sad and some of them wept bitterly, except Yuan Shao, who was so calm and easy-going, and did not change his usual manners at all, that he made the people feel a little bit more at ease.
Then Yuan Shao led an army to counter-attack. The rebel army was defeated and retreated south to Zhaoge(朝歌), where Yuan Shao led his army to arrive later, and after five days of fierce fighting, Yudu, together with more than 10,000 of his men, was killed.
Then Yuan Shao led the army along the deer intestine mountain, all the way to the north, eliminated many other yellow turban uprising forces, killed more than ten thousand people.
Yuan Shao then encountered Zhang Yan(张燕), the main force of the Black Mountain Army, at Changshan(常山present day Shijiazhuang石家庄), the two sides started a large-scale battle, which lasted for ten consecutive days, with both sides suffering heavy deaths and injuries, then each side rested its troops.
In 195 AD, Zang Hong(臧洪), the governor of Dongjun commandery(东郡) under Yuan Shao, announced that he had broken with Yuan Shao and severed his affiliation. Yuan Shao personally led a mighty army and besieged the city for a year. The city was cut off from provisions, and Zang Hong was killed after the city broke down.
In the same year, Xianyu Fu(鲜于辅) and others, the old troops of Liu Yu(刘虞), the former governor of Youzhou, united with Wuhuan(乌桓a nomad in the north of China) to attack Gongsun Zan. Yuan Shao took advantage of the opportunity to send his general Qu Yi(麯义) to combine his troops with Xianyu Fu's, for a total of 100,000 men to attack Gongsun Zan, defeating Gongsun Zan's main force at Baoqiu(鲍丘), beheading more than 20,000 of them, while Gongsun Zan retreated to Yijing(易京) to hold on.
The city of Yijing was very strong and difficult to conquer, Qu Yi's army ran out of food and had to withdraw, Gongsun Zan took advantage of the situation to pursue and defeat Qu Yi.
Although Qu Yi was attacked on the way to withdraw , it was no longer harmful. After this defeat, Gongsun Zan could be said to have been devastated, he was already lost.
Yuan Shao then sent his nephew, Gao Gan, to take over Bingzhou, which had been plagued by the South Xiongnu and plundered by the Black Mountain Army, by appointing him as the inspector of Bingzhou.
Yuan Shao also recommended his eldest son, Yuan Tan(袁潭), to be the Provincial Governor of Qingzhou(青州) and to garrison in Pingyuan. Yuan Tan was fierce and good at fighting, and soon defeated Gongsun Zan's general, Tian Kai(田恺), the former inspector of Qingzhou, expelling Tian Kai back to Youzhou.
In the spring of 196 A.D., Yuan Tan attacked Kong Rong(孔融a famous literati), the governor of Beihai(北海), to the east. Kong Rong was good at writing poems, but not good at fighting, so Yuan Tan won the battle and Kong Rong fled to Xuchang(许昌) with only himself, while his wife and children were captured.
Afterwards, Yuan Tan continued to march, swept away many of the Yellow Turbans along the coast, finally occupying the whole of Qingzhou, thus the two provinces of Qingzhou and Bingzhou officially belonged to Yuan Shao.
In 198 A.D., Yuan Shao, who was determined to completely destroy Gongsun Zan, personally led a mighty army to attack Youzhou, was invincible all the way, soon encircled Yijing, some of Gongsun Zan's generals surrendered, some collapsed, while the soldiers were even more unmotivated to fight.
Gongsun Zan felt that things were not going well, so he sent his men to break out of the city and ask for help from the Black Mountain Army, agreeing with the rescuers to set up a fire as a signal to pincer attack Yuan Shao.
Unexpectedly, the letter of asking for help was intercepted by Yuan Shao. Yuan Shao made a plan and set fire to the city as scheduled, Gongsun Zan thought that help was coming and led his troops out of the city to attack, which was defeated by Yuan Shao and he had to retreat to the city again.
Then Yuan Shao dug a tunnel to the underground and burned down the platform by burning the pillars. Gongsun Zan, knowing that he was already lost, strangled his wife and children and prepared to set himself on fire, when Yuan Shao's soldiers arrived and beheaded Gongsun Zan, who had failed to commit suicide, while all his troops were annexed by Yuan Shao.
By now, Yuan Shao finally started from a small Bohai commandery and became the strongest warlord in the country with hundreds of thousands of troops in the four provinces of Jizhou,Qingzhou,Youzhou,Bingzhou.
At this time is the peak of Yuan Shao, not only the territory is vast, strong soldiers and horses, and sufficient food, no trouble, the generals are all experienced in hundreds of battles, strategists and civil officials are all the then famous, can be said to be majestic in the whole country.
So in the same year that Gongsun Zan was destroyed, 199 A.D., Yuan Shao gathered 100,000 elite infantry and 10,000 cavalry, stood on the north bank of the Yellow River, waiting for an opportunity to cross the river and fight with Cao Cao, and a large-scale war between Yuan and Cao began.