"will have avoided" vs. "will avoid" in the following context

Question

Example with a context:

Asked if France would join the United States in providing such equipment to the Ukrainian military, Hollande said "the option of negotiation, of diplomacy, cannot be extended indefinitely."

But the French President emphasized that first, both he and Merkel were working together toward a proposal they hope will be acceptable to all parties in the conflict.

"We want to develop a German and French negotiation document, along with Ukraine and also with Putin, he said.

"If we succeed, we will have avoided an escalation of the conflict. If we fail, and this hypothesis remains, what will be said? That France and Germany will have done everything they could do to take action to resolve the conflict."

To me, it sounds like there would be absolutely no difference if we used either one. What do you think?

Answer 1

There is a difference, because of the conditional.

If we succeed, we will have avoided an escalation of the conflict. If we fail, and this hypothesis remains, what will be said?

If we succeed → at that point in time "avoided" is in the past, therefore "we will have avoided".
If we fail → at that point in time "said" is in future, therefore "what will be said"? (in the future after the failure).

Examples:

If you pass the exam, I will buy you a cake to celebrate. (Order of action is first passing the exam then buying cake)
If you pass the exam, you will have proven him wrong. (Passing the exam is equivalent to proving him wrong)

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The same is true of will have done everything, although I find the wording a little clunky. It works here because it's speaking of the future - we have not yet done everything, but if we try and fail, we will have done everything.

When speaking of a past event, it would be normal to instead say, as you suggested, "France and Germany did everything they could do to take action to resolve the conflict".