[合「あ」]う => To do A together/mutually N4
Secondary Verb
を[込「こ」]めて => Put A into it N2
Will, Decision, “Doing”
にひきかえ => In contrast to A N1
Comparison/ Exchange
[必要「ひつよう」]はない => It is not necessary for A to be done N2
Needs, Requirements