The grasslands.
Half a year earlier, Meng Tian, the great general of Northern Li, had led his army north. The Liao Kingdom had held out for only half a month before declaring its submission.
From then on, both the Jin Kingdom and the Liao Kingdom, north of Great Song, had fallen in succession. The many foreign tribes nearby, such as Tubo and Western Xia, had either submitted like Liao and Jin or migrated farther west, seeking the protection of Goguryeo and the Turkic Khaganate Kingdom.
As for those unwilling to submit who had not fled, their fate needed no elaboration: Meng Tian had naturally led his army to trample them flat.
Afterward, without stopping to rest his horses, Meng Tian had continued marching west, preparing to destroy Goguryeo and the Turkic Khaganate Kingdom as well.
The first to bear the brunt was Goguryeo.
Goguryeo lay northeast of Great Sui. Its territory stretched two thousand li from east to west and over a thousand li from north to south. With a population exceeding four million, it was already a sizable vassal kingdom.
During the wars between the various states several hundred years earlier, Goguryeo had seized the opportunity to rise, rapidly expanding and growing into a major threat in Great Sui's northeast.
Later, to develop further, Goguryeo had continually expanded toward Great Sui's northwestern regions, even nibbling away at its northeastern borderlands and repeatedly harassing its people.
Unable to endure any more, and with the aristocratic clans of Guanlong growing increasingly powerful at the time, Yang Guang had launched three campaigns against Goguryeo regardless of the cost, intending to weaken those clans.
Unfortunately, he had still failed in the end.
Although obstruction and sabotage by forces within Great Sui had been the main cause, Goguryeo's strength could not be underestimated either.