Semper Fi, General Mattis
Both battlefields were declared "hopelessly lost" by the experts, and yet the Marines won in both. Indeed, they won so thoroughly that they were frustrated at the lack of action. Al-Qaeda ran from them in Anbar, and the Taliban ran from them in Helmand. The poor Marines were reduced to building roads, schools, and hospitals, and managing microloans to the locals. That is not what the Marines are trained to do, and they do not enjoy it very much. They are trained to fight and win.
The American retreat is a mistake; it invites future conflict under conditions chosen by our enemies, thereby guaranteeing needless casualties and perhaps even defeat. And we won't have General Mattis to lead the next assault. He tried very hard to focus our attention on Iran, but to no evident avail. So we're just as happy to have our kids off the battlefield. Soldiers' parents are gripped by two intense emotions: great pride, and terrible anxiety. Having men like Mattis in command positions eases the anxiety and intensifies the pride. The current crop of political leaders, the Obamas, the Hagels, and the Kerrys, just intensify anxiety. They recoil from conflict, and beg our enemies for understanding and forgiveness of imagined American sins. As Churchill famously said of Chamberlain, they choose "dishonor" and will have war.
It's entirely appropriate for General James Mattis to retire at this moment. Godspeed, sir, and Semper Fidelis.