Their policy was staying in Osaka-jo Castle surrounded by double moats plus huge sobori (moats around a castle town) and fortified firmly, exhausting the Tokugawa army and gaining favorable pacification.
二重の堀で囲われさらに巨大な惣堀、防御設備で固められた大坂城に立て籠もり、徳川軍を疲弊させて有利な講和を引き出そうという方針である。