The resulting silting was so heavy that after the Yellow River changed back to its northerly course for the most recent time in 1897, the geography of the Huai River basin was changed significantly by the creation of new high lands, lakes, and the built-up silt of the Yellow River's historical southern course. As a result, water from the midsection of the river could not easily flow into the lower section, while water in the lower section could not find an outlet to the sea. The problem worsened in the Second World War, when the Chiang Kai-shek government, in an attempt to check the pace of the Japanese invasion, flooded the lower Huai basin by opening the Yellow River's southern levee.