I'm not necessarily looking for a literal translation, rather, I want to preserve as much of the connotation as possible.

First, I decided that the verb I would use to 'to stand', would be 'restabare', since it carries both the military connotation of 'to stand firm', and in classical Latin, the connotation of 'to oppose' or 'to remain' (as against adversity in general).

I'm less happy with the verb for 'to fall' - the best I could come up with is 'succumbere', since in Classical Latin, it carries the connotation of 'to submit'/'to yield', as well as 'to sink down'.

Once I settle on a verb, I can think of two ways to translate this. The first is to use the ablative of attendant circumstances or ablative of specification:

Succumbantis (omnibus) [cum] alis restabo - literally, 'I will stand with (all) others fallen' (The 'cum' is optional when using this form of the ablative, but is generally placed between the adjective and the noun).

or

Cum alii succumbant restabo - I will stand when others fall (the subjunctive verb with 'cum' rather than the indicative because the clauses have a causal link).

or, possibly using the poetic form of the perfect tense:

Cum alii succubuere restabo

EDIT: I believe I'm now going to choose between

1) Succumbentis omnibus restabo

2) Cum succumbant restabo