To begin with, the first cause is the Capulets servants' inability to endure the Montague at sight. As a result they fought for the honor of their house. In the early opening scene, the Capulet servants start taunting and asking if the Montague servants would quarrel. (Act 1, Scene 1, Line 51) in which the Montague servants responded not. (Act, Scene 1, Line 52) Despite the fact that the Montague servants are not looking for trouble the Capulets servants drew their swords anyways. (Act 1, Scene 1, Line 61). This clearly shows that the Capulet servants have valued their honors too highly in the name of their house for they intend to fight the Montagues without any second thoughts.
In addition, Tybalt refuses to keep peace despite Benvolio who does not intend to fight. Consequently, Benvolio has no choice but to engage in combat with Tybalt. At the beginning of the play, Tybalt makes it clear that he is against peace and will fight anyone who stands in his way (Act 1, Scene 1, Line 68). Benvolio, on the other hand hesitated to fight and said, "I do but keep the peace." (Act 1, Scene 1, Line 67) In the end Tybalt calls him a coward and they fight. (Act 1, Scene 1, Line 70). Tybalt clearly has been fighting for his honor under Capulet's name.
Furthermore, Capulet demands for a sword after spotting Montague. This provokes Montague to try and