The main focus of this article is upon how Chosǒn pursued ‘the ground and maritime joint defense’ as the main part of its anti-Japanese strategy and as the principle of its military collaboration with the Ming by actively taking advantage of its geographical terrain bridging Ming and Japan via Yellow Sea/Southern Coast. From the first half of 1593 to the first half of 1594, when the Ming army stationed in Chosǒn, the Chosǒn court proposed a joint operation between the Ming ground forces and the Chosǒn maritime forces for a complete repulse of the Japanese invaders who camped in the Southern Coast and sought to enter into Chǒlla Province and Yellow Sea. And, from the second half of 1594 to the second half of 1596, when the Ming army withdrew from Chosǒn, the Chosǒn court devised plans of a combined operation between the Chosǒn navy and the Ming navy in order to carry out a sea blockage and destroy the Japanese armies within Chosǒn. What is more, this ground and maritime joint defense plan, emphasizing the strategic importance of Chosǒn in geographical terrains, also concerned such practical matters as how to enhance firepower, replenish military strength, and increase the number of battleships. At this juncture, we can rethink the way Chosǒn strove to strengthen its anti-Japanese counterattack and to overcome the unprecedented national crisis. This approach will enable us to explore complex and multilayered contexts in a wider analytic methodology that redefines the war as an international war in East Asia.