箭在弦上的英文：
[Literal Meaning]
arrow/on/string/on
The arrow has already been on the string.

[解释]
箭已放在弦上。比喻为形势所迫，不得不采取某种行动。

[Explanation]
Actions must be made and there can be no turning back.

[例子]
现在的形势已经是箭在弦上，我们必须立刻采取行动，否则就来不及了。

[Example]
There can be no turning back, and we must take actions now. Otherwise it will be too late.

The arrow is already fitted to the string—have to do something
箭在弦上

The arrow is already on the string;it must happen;a point of no return
箭在弦上

An arrow fitted to the bowstring cannot avoid being discharged.
箭在弦上，不得不发。