Demand that

[Chicken Sandwich]

They demanded that the military government free all political prisoners.

Would it be incorrect to say

They demanded that the military government would free all political prisoners.

?

Somehow this sounds better to me then the first sentence. However, in these kind of phrases "would" is omitted, so I assume that it's either incorecct to include would or it's just less common.

Thank you in advance.

[5jj]

They demanded that the military government free all political prisoners.

That is fine. 'Would' is not possible.

[Raymott]

Would it be incorrect to say

?

Somehow this sounds better to me then the first sentence. However, in these kind of phrases "would" is omitted, so I assume that it's either incorecct to include would or it's just less common.

Thank you in advance.

I'm not sure if "would" is impossible.
In fact if the context suits, the sentence with "would" is not wrong.
"The guerillas demanded that the military government would free all political prisoners, if they (the guerillas) stopped the incursions." That is, they are not demanding the freeing unconditionally. But they are demanding that government would do it under certain conditions.

This construction is also sometimes used with "should".
"They demanded that the military government should free all political prisoners."
I consider this much less correct than "would" used correctly.

[5jj]

I'm not sure if "would" is impossible.
In fact if the context suits, the sentence with "would" is not wrong.
"The guerillas demanded that the military government would free all political prisoners, if they (the guerill as) stopped the incursions." That is, they are not demanding the freeing unconditionally. But they are demanding that government would do it under certain conditions.

This construction is also sometimes used with "should".
"They demanded that the military government should free all political prisoners."
I consider this much less correct than "would" used correctly.

We differ here.

I think that 'would' is possible with said, claimed, suggested and other verbs, but not with 'demanded, requested, asked, + that. I consider the version with should marginally acceptable with demanded. But that is just my opinion; I look forward to seeing what others think.

[Tdol]

This would also work for me:

They demanded that the military government freed all political prisoners.

[Raymott]

This would also work for me:

Now that sounds weird to me. They demanded that the military had already done something? Well, you probably mean "freed" to be the subjunctive. It might be right, as might 'would' and 'should', but it still sounds weird. I think there are regional habits in the use of this sort of expression.

[Tdol]

It could well be regional.

[Bennevis]

should does the trick for me

[shannico]

I think there are three options which convey the obligation implied by verbs such as demand, request, order, recommend etc...
1) They demanded that the military government free all political prisoner.
2)They demanded that the military government freed all political prisoners.
3)They demanded that the military government should free all political prisoners.

In both n.1 and n.2 the base form and the past simple work as a subjunctive form.

I would rule out "would".