Choshu Domain, where reformists and conservatives were in a power struggle, carried out the exclusionist policy, bombarding a foreign vessel sailing through the Bakan Straits with home-manufactured cannons in May 1863.
藩内改革派と保守派が藩政の主導権を争っていた長州藩では、5月、馬関海峡を航行中の外国船を自藩製の大砲で攻撃して「攘夷」を決行した。