Ever though the authentic history on the first war between Kokurye and Sao-dynasty is not good enough. there are many kinds of suppositions and debates upon this war in the current history books. This study gathered current and old historical records and analyzed the next five results. First. Chang-rna (the rainy season of Korea) had a great effects on the battle. Second. unlike the authentic history. the war seized not only the effect of Chang-rna but also the battle action. Third, battle field is supposed have been in Im-yu-goan. Fourth, the Kokurye force did not come across the Chang-rna but made a great victory by using it intentionally. Fifth. there was a great strategist at that times whose name was Kang-Ie-Sik. But. in spite of many positive records there is little doubt on that he was the commander of the Im-yu-goan battle.