I was rewatching the anime where Garp goes to save Koby and I realised that he was leading the frontier (obviously). But for Birdie’s attempted rescue in Captive, did Garp have any opinion or contribution? Also did he have any after thought when the marines reported her dead after Koby returned?
Hi Anon! Yeah, that episode is amazing.
At the time of Captive, Garp was in the East Blue (or somewhere similarly far away), so he didn't have much of a role there. He probably would have helped Koby if he asked.
Birdie wasn't really reported dead once Koby and Helmeppo got back, they told the truth about what happened, it's just that sending battleships against the Kid Pirates to retrieve one marine that was probably already killed was never deemed a priority. I imagine Koby and Garp had little to no contact at the time.
Garp does appear in Mission Dressrosa and we have a glimpse on his view on the whole situation. He tries to cover up birdie's defection and warn Koby before Sakazuki catches wind of it.
To be fair, with Aokiji being Garp's former pupil, birdie should have had some sort of protection from the Vice Admiral after Aokiji left. But the truth is that Garp was also traumatized by Ace's death: he spent time in the East Blue and almost left the Marines. Meanwhile the fight for the new Fleet Admiral occurred. So he was not there for anyone, and by the time he took an active role in the Marines again, birdie's position was already re-defined.
Garp doesn't strike me as the type that reaches out first to people struggling (unless maybe it's a life/death situation), and birdie isn't one to ask for help, so the two never developed a relationship at any point.