君の援助が

your help

→ 君
phrase Rare #39,037
your help 君 is a familiar or casual way to say “you.” The particle が marks “your help” as the subject of the sentence.
JA: 君の援助が必要です。
EN: Your help is needed.

君の援助が無かったなら私は事業に成功しなかっただろう。

If it hadn't been for your help, I wouldn't have succeeded in business.

我々の計画の成功には、君の援助がどうしても必要だ。

Your assistance is absolutely essential to the success of our plan.