On 16 February 1637, Qing troops landed on Ganghwa Island and occupied Ganghwa Castle. According to the conventional narrative, a few Joseon warships bravely fought in vain to deter the enemy from crossing the shallow, narrow Yeomha Waterway while the main fleet cowardly ran away. A close investigation of firsthand accounts of this battle, however, reveals that no Joseon warships blocked this waterway during the Qing ferryboats’ advance. Here the question arises: What kept Joseon’s naval warships from entering this waterway while the Qing boats were able to cross? In exploring possible answers, Joseon's records indicate that the presence and timing of strong tidal currents might have been a crucial obstacle to the warships’ movement. Given the substantive differences in accounts between Joseon and Qing, this paper attempts to verify which account is more accurate, by hindcasting the paleo-tidal currents and tides (PTCT) of the day via two methods: a conventional harmonic prediction method and a correct tidal species modulation with tidal constant correction method. The PTCT results in general, and the timing of the hindcast high tide and slack water period (around 10:30 am) in particular, tally with the Joseon account. Moreover, our results provide new evidence to support the detailed reconstruction of events surrounding the Qing troops’ 1637 landing operation.