Japanese: 公武合体 (Koubu Gattai)
Kôbu Gattai was a political "theory" developed during the Bakumatsu period of political unity between the Bakufu and the imperial court. Under the Kôbu Gattai vision, the highest ranking lords of Japan (Daimyo, Bakufu officials, and the court) were to work together for the good of Japanese society. The purpose was to get imperial legitimacy for decisions made by the han lords and the Bakufu, however the reality was that it was ineffectual due to the competing interests of the participating lords - namely Shimazu Hisamitsu, Matsudaira Shungaku, Yamauchi Yôdo, Tokugawa Yoshinobu, Matsudaira Katamori, Date Munenari, and before his death, Shôgun Tokugawa Iemochi, among others.
In 1861, in perhaps the most significant show of court-bakufu unity, Shôgun Iemochi married Princess Kazu-no-Miya who was a sister of Emperor Kômei. The Kôbu Gattai marriage didn't last very long because both Iemochi and the Emperor died within 5 years.
The lack of unity among the lords constantly negated any effective decision-making, and eventually lead to its failure.