The Ambition of the Sui Dynasty that Swallowed Southeast Asia, Falling into Goguryeo's 'Empty Castle' Trap

In 597, a state letter from the Sui dynasty arrived before King Yeongyang of Goguryeo. The content was clear: a threat to submit as a vassal state. While the Sui dynasty pressured them, saying, "If you sincerely repent, we will give you a chance," Goguryeo's choice was different. The Goguryeo army launched a preemptive strike toward the Sui dynasty. It was the moment a massive frontal confrontation between the Korean Peninsula and the continent began.

The Ambition of Emperor Yang of Sui to Pierce the Continent's Main Artery and the Hegemon of East Asia

At the time, the Sui dynasty was a true empire. From the year after his accession, the second emperor of the Sui dynasty, Emperor Yang of Sui, mobilized tens of millions of people over six years to complete the Grand Canal of China. This massive waterway, flowing 1,800km from Hangzhou to Beijing, became the main artery of China. Through this canal, Emperor Yang of Sui pulled abundant resources from the south to the north, and based on this, he reigned as the hegemon of East Asia by conquering Linyi in Vietnam, the Ryukyu Kingdom in Okinawa, and the Majaka Kingdom on the Malay Peninsula.

There was only one task left for Emperor Yang of Sui, who had even forced the Göktürks, a rising power in the north, to submit. In the stone stele containing records of the funeral of the Göktürk king at the time, the name 'Boekli' appears, which means 'Goguryeo' in ancient Turkic. Emperor Yang of Sui encounters a Goguryeo envoy while visiting a Göktürk tent. At that time, Goguryeo was the only country that did not kneel to the Sui dynasty. Fearing that northern ethnic groups would break away if Goguryeo were left alone, Emperor Yang of Sui decided to attack Goguryeo to complete his authority as the master of the world.

The Iron Wall of Liaodong, Goguryeo's Defense System and the Advance of the 1.13 Million Great Army

Goguryeo chose war instead of submission. At the center of this was Liaodong Fortress, the stronghold that controlled the entire Liaodong region. Looking at the traces remaining in present-day Zhengyao City, Liaoning Province, China, Goguryeo built a double-structured wall consisting of an inner and outer fortress and protected the castle with moat facilities using the water from the Taizi River. In particular, the 'chi' structure, unique to Goguryeo, which protruded parts of the wall to attack and trap enemies from multiple directions, was a very powerful defense system.

In January 612, Emperor Yang of Sui led a massive army of 1,133,800 people and advanced toward Liaodong Fortress. Emperor Yang of Sui prepared thoroughly, such as constructing 300 ships in Yuzhou, Shandong Province, for the war. At the time, the labor for building this massive fleet was so grueling that people experienced the tragedy of cutting off their own hands and feet to avoid conscription. Emperor Yang of Sui planned to directly strike Pyongyang Fortress, the capital of Goguryeo, by organizing not only a land army but also a detachment of 300,000 people.

The Trap in Pyongyang Fortress, the Luring Operation that Crushed the Detachment

The strategy of the Sui dynasty was to deploy the navy to Pyongyang Fortress first to occupy the castle before the land army. The navy arrived at Pyongyang Fortress before the land army and advanced into the empty castle. However, this was a trap dug by Goguryeo. The Goguryeo army left the castle empty to lure the Sui dynasty army, then launched a surprise attack. The naval detachment, which was attacking the castle alone, fell into Goguryeo's luring operation and was defeated.

As the navy retreated, the Sui dynasty land army, which had advanced to Pyongyang after crossing the Yalu River, faced a fatal problem. It was that they ran out of food. The situation was so bad that the generals leading the 100,000-strong army despaired, saying, "If we cannot destroy this weak enemy, how can we face the Emperor?" The Goguryeo army employed a strategy of luring the Sui dynasty army again by pretending to be defeated, continuing a desperate struggle against the massive army.