Once the Edo bakufu decided to dispatch its punitive force against Choshu Domain for the Kinmon Incident, Choshu Domain enforced a naval blockade as its countermeasure at Kanmon-kaikyo Strait which was under its control, and this blockade inevitably close off the sea route from the Tohoku and Hokuriku regions to Osaka via Kanmon-kaikyo Strait and Seto Inland Sea.
禁門の変によって長州藩追討が決定されると、関門海峡を支配する同藩の海上封鎖によって東北地方・北陸地方から同海峡・瀬戸内海を経由して大坂に向かう航路の封鎖が確実となった。