A study of the river is essential to an understanding of the battle. Opposite Wiju the Yalu and the Ai-ho flow through a broad delta bounded on the North by a steep and rugged mountain range that descends West of Antung into small hills and cultivated flats. The rivers separate into several streams and form many islands over which are scattered tiny hamlets. Close to Wiju, between the Yalu and a branch of that river, lies the island of Kontonto, seamed with deep dongas in which Russian riflemen were concealed. North of Kontonto, beyond the main stream, is the island of Wozakto, West of which, between branches of the Yalu and the Ai-ho, rises Tiger Hill, a bold promontory three thousand mètres from Wiju. Enclosed by the same branch of the Ai-ho and the main stream of that river stretches another delta known as Chonchagtai, whereon the most conspicuous building is a temple surrounded by a red wall. West of this island flows the main stream of the Ai-ho, which passes within one thousand mètres from Conical Hill before it approaches Chiu-lien-cheng. Near to the Korean shore the Yalu and another of its branches form the island of Nanzato. The South-west of the delta is opposite Antung, where the river is five hundred mètres wide and is deep enough to allow small coasting vessels to steam within three or four miles from the town. At the Northern extremity of the delta lies the island of Kulito. In considering the tactical possibilities of the river it is most important to keep in mind the fact that at Kulito the main stream of the Yalu runs along the Russian side, while near Wiju it flows along the Japanese side, making a sharp turn almost North and South and bending again toward the South-west. Tiger Hill and the heights to the North between the main streams of the Yalu and the Ai-ho, stand next in tactical importance. Would these mountains admit of any big movement of troops? The experience of 1894 was of little value, seeing that in the Chinese War only one regiment crossed these mountains. At that time the Japanese were of opinion that the heights were useless for offensive purposes, since they were steep and rugged and had no paths running East and West. Natives declared that only men and pack ponies could traverse them, and that at one or two places alone could roads be made with extreme labour owing to the hardness of the rock. These difficulties, so far from deterring General Kuroki, were a strong incentive. If these mountains were inaccessible then they were the very quarter from which to surprise the enemy and turn his flank.