Learn Russian: Наша солидарность важна, даже если борьба будет долгой. - Our solidarity is important, even if the struggle is long.

The structure даже если (even if) can take either the indicative (normal tenses) or the subjunctive (using бы). Here, it uses the future indicative (будет) because the speaker views a long struggle as a real, distinct possibility in the actual future. If they wanted to express a purely hypothetical or highly unlikely scenario ("even if the struggle were long"), they would use the subjunctive: даже если бы борьба была долгой.

Why do we use the short adjective "важна" here instead of the full form "важная"?

Short-form adjectives like важна are used exclusively as predicates (the "is [adjective]" part of the sentence). While you could technically say наша солидарность важная, the short form sounds more formal, categorical, and abstract. This elevated tone fits perfectly with concepts like "solidarity" and "struggle."

Why is the adjective "долгой" in the instrumental case rather than the nominative ("долгая")?

When an adjective follows the future tense of the verb "to be" (будет), it typically takes the instrumental case (долгой). This is a standard rule in Russian for describing a state or characteristic in the future or past, especially when it implies a temporary state or a condition that develops over time.