Estar al pie del cañón
 

In English please? Estar al pie del cañón es estar para alguien cuando te necesita o viceversa.

I'll be there.

Your wish is my command.

You can count on me.

ANd to say he is always there when I need him, His wish is my command ?

no, it would be: "my wish is his command.".

hermit

It means when a person needs to be already in the moment.

I don't know if you are agree with my commentary, but it is relationed in the politic.

I mean if a political needs a person who's already in the things that the political needs to he does it during his campaigner, therefore he will ask him (Debes estar al pie de canon durante las campanas electorales.)

You can also say I'm at your beck and call.

I'm at your beck and call. :thumbsup: He's at my beck and call.
I'm there for you. :thumbsup: He's there for me.
I'm/He's ready and able.
I'm/He's ready and waiting.
I've got you covered. He's got me covered.
I've got your back. He's got my back.

estar alguien al ~ del cañón.
1. loc. verb. coloq. No desatender ni por un momento un deber, una ocupación, etc.

www.rae.es

He's always at it. He keeps at it.
He never rests.
He's a workaholic.
He keeps on it.