Yu Wenyong's reforms greatly increased number of registered households in Northern Zhou Dynasty, gradually enriched finances, and increased size of army from 100,000 to 200,000 men. However, Northern Qi Dynasty at that time was very stupid, and it was on verge of decline. It was said in history that “the Qi family is stupid and cruel, with many political parties, selling officials in prisons, mercenaries, promiscuity, and do not harm good people. The situation is terrible, We cannot outweigh disadvantages". At same time, Northern Qi failed to resolve Xianbei-Han conflict in six cities, which hastened its decline.
In order to destroy Northern Qi more quickly, Yu Wenyong decided to form an alliance with Nan Chen. In 573, Northern Zhou Dynasty invited Chen Dynasty to attack Northern Qi Dynasty together, so Chen Xu went to Northern Qi Dynasty, defeated Qi army in Xuzhou, and regained land of Huainan. However, in reality, Chen Xu was just a successful king. He was content with just painting Huai River and defending himself, so he did not go further north to attack interior of Central Plains. This is exactly what Yu Wenyong wanted to see.
Yu Wenyong of Northern Zhou Dynasty sent troops in 575 to unify north. At this time, Chen Xu repented, so he sent troops to Shandong, but was defeated by Northern Zhou Dynasty, 100,000-strong army was destroyed and suffered heavy losses. In second year, land of Huainan was largely occupied by Northern Zhou Dynasty.
In 575, Yu Wenyong mobilized 180,000 troops to attack Northern Qi Dynasty. Among them, Yu Wenyong personally led six armies to capture Heiying (Mengjin), and Yu Wenxian's vanguard army also captured eastern and western cities of Luokou. Subsequently, army of Northern Zhou dynasty was unable to besiege Luoyang and Jingcheng (Meng County) and was forced to retreat. At this time, Nancheng army was restoring its strength in Huainan.
In 576, Yu Wenyong led an army of 140,000 men to attack Shanxi in an attempt to capture Taiyuan, an important military city of Northern Qi Dynasty, and then bypass Central Plains. When Northern Zhou army captured Pingyang, Northern Qi emperor Gao Wei was hunting in Tianchi (Mount Guanchen). When news came of Northern Zhou's attack, his concubine Feng Shufei "Please kill another round". Due to untimely military actions of Northern Qi Dynasty, Pingyang was quickly captured. After that, Northern Qi Dynasty army went south to prepare for decisive battle with Northern Zhou Dynasty, and Yu Wenyong withdrew main force to pass, leaving 10,000 elite soldiers to defend Pingyang. So, 100,000-strong army of Northern Qi Dynasty began siege of Pingyang, and after a month of siege, Pingyang was still strong.
Seeing that Northern Qi army was depleted, Yu Wenyong sent 80,000 elite soldiers to fight Northern Qi army. The armies of both sides took up positions in Pingyang, a "stalemate". The Northern Qi army then moved south, and two armies engaged in battle. At critical moment, eastern wing of Qi army retreated slightly. So, Concubine Feng Shu and others thought that Northern Qi Dynasty would fail, so they urged Gao Wei to leave Gaoliang Bridge. Gao Wei complied and ordered a retreat, resulting in a loss of morale in army. Yu Wenyong took opportunity to attack furiously, and Northern Qi "the military capital was first battle, hundreds of miles away, and mountains were abandoned." in Shanxi one by one, and main forces of Northern Qi dynasty were almost destroyed.
At this time, Gao Wei, Emperor of Northern Qi Dynasty, tried to flee to Turks, but failed, and ministers of Northern Qi Dynasty surrendered one by one. In 577, Yu Wenyong led an army to capture Yecheng and Gao Wei was captured. Since then, Northern Qi dynasty has perished, and North has declared unification. When Northern Zhou Dynasty sent large-scale troops, Southern Chen army also launched a second Northern Expedition in an attempt to share Kanto with Northern Zhou Dynasty. Soon Northern Zhou's army and Southern Chen's army clashed with each other, and Southern Chen's army was smashed to pieces, and soon whole land of Huainan fell into Northern Zhou's hands. Nan Chen actually costs nothing to carry water from a bamboo basket.
To focus on destroying Northern Qi Dynasty, Yu Wenyong continued to pursue a unified policy towards Turks. With unification of north, Yu Wenyong was ready to head south in one fell swoop to destroy Nancheng. However, in 578 Turks attacked Youzhou, so Yu Wenyong led Northern Zhou army on Northern Expedition. But on way to Northern Expedition, death of Yu Wenyong failed to realize his desire to "pacify Turks and stabilize south of Yangtze River."Conclusion
Despite this, Yu Wenyong can still be called most prominent emperor of Northern and Southern Dynasties. Northern History noted that “ it is hard work, dedication and hard work; labor is first of soldiers, living with frugality of same husband; repairing government of a wealthy country, art of strengthening army; taking advantage of provocations of people, he went along path of heaven and died. A few years later, Dasunsi got together”. Although he did not unify entire country, he conquered two-thirds of world, initiating unification of Emperor Wen of Sui Dynasty. In addition, he sent troops to attack Tuyuhun, weakening its national power, and set stage for subsequent destruction of Tuyuhun under Sui and Tang dynasties. The Book of Zhou says, “ After destruction of Qi, I wanted to use my troops to become extremely powerful, pacify Turks, and populate Jiangnan. In a year or two world will come together".