(I'm not quite done with Plutarch yet!)
Both Alexander and Caesar gained political power through combat prowess. Espescially Caesar who used his triumphs to gain political fame and used the spoils of war to enrich his soldiers and followers. (And by the way, when I say 'triumph', I don't just mean a 'win'. A Roman triumph was a kind of victory parade that sanctified a military win.) This lead me to think about our modern way of choosing leaders.
In the 18th and 19th century, the United States chose a number of Presidents because of their war prowess. Washington, of course, and then Jackson and Grant are obvious examples, and there are many others. Once you get to the 20th century the war heroes start to thin out though. Of the men who gained fame through war and then became President, I count Teddy Roosevelt, Eisenhower and JFK. Many others served, but those were the ones who I think best fit the category.
JFK was elected more than 50 years ago. We still hear generals names floated about not as seriously as in the past. I don't know if the national taste for 'warriors' has diminished, though I suspect it has. I also suspect that today's soldiers are more anonymous than they were in the past. Possibly the modern political party makes it harder for someone to take high office as a second career (though Obama's short political timeline contradicts this).
It may also be a quirk in timelines. I don't have any numbers before me but there are many returning soldiers from Iraq and Afghanistan who are now running for seats in the House of Representatives. Maybe we'll have a string of them in the Presidency some time in the future. Who knows?