The first one stemmed from territorial issue of Numata territory due to reconciliation of the Tokugawa clan and Hojo clan, and it can be considered as a territorial battle (ego battle) between the Tokugawa clan who requested the hand over of the Numata territory and the Sanada clan who rejected it.
第一次は徳川氏と北条氏の和睦に伴う沼田領の帰属問題に端を発し、北条氏への沼田領引き渡しを求める徳川氏とそれを拒絶する真田氏の領地争い（意地の張り合い）の色合いが濃い。