Are you kidding?
Even at 50% casualties, this was a major victory on Henry and Gallia's part. It was stated that Gallia outnumbered the elves 2:1, and then suffered 50% losses to the elves 28K, Henry achieved an unheard of 1:1 exchange against the elves without the use of bullshit void magic or literal nukes. Recruitment will likely go through the roof as people who will have inevitability lost friends and family, or are seeking glory under a commander that could bring miraculous victories sign up for the army.
Henry has been gearing Gallia for war for most of this story (years), replacing lost equipment like uniforms, weapons, ammunition is going to be trivial. Replacing ships is a more daunting task, but possible under wartime production with the looming threat of elves.
And with a population base of millions of people, replenishing the manpower lost is only a question of training time, a few months if he wants to be thorough, a few weeks if rushed.
-SK