Concurrently, because there had been no decisive encounter at sea, the Japanese decided to send more troops to Korea. Early in September, the navy was directed to support further landings and to support the army on Korea's western coast. As Japanese ground forces then moved north to attack Pyongyang, Admiral Ito correctly guessed that the Chinese would attempt to reinforce their army in Korea by sea. On 14 September, the Combined Fleet went north to search the Korean and Chinese coasts and to bring the Beiyang Fleet to battle. On 17 September 1894, the Japanese encountered them off the mouth of the Yalu River. The Combined Fleet then devastated the Beiyang Fleet during the battle, in which the Chinese fleet lost eight out of 12 warships. The Chinese subsequently retreated behind the Weihaiwei fortifications. However, they were then surprised by Japanese troops, who outflanked the harbour's defenses in coordination with the navy. The remnants of the Beiyang Fleet were destroyed at Weihaiwei. Although Japan turned out victorious, the two large German-made Chinese ironclad battleships ("Dingyuan" and "Zhenyuan") remained almost impervious to Japanese guns, highlighting the need for bigger capital ships in the Imperial Japanese Navy. The next step of the Imperial Japanese Navy's expansion would thus involve a combination of heavily armed large warships, with smaller and innovative offensive units permitting aggressive tactics.