To suffer a minor defeat or failure, but achieve a larger, more important, or overarching success or victory over time. The phrase is often split into two halves across different parts of a sentence to achieve its meaning. We may have lost the battle for now against this unjust law, but we're confident that we will win the war when it comes before the Supreme Court next month. By forcing the enemy to expend so many troops and resources, they'll be too depleted to defend our other avenues of attack, so while we lost this battle, we'll now be able to win the war.