The legendary defense of the Spartans at the "hot gates" of Thermopylae has gone down in military history as one of the greatest last stands.
But what if 300 Marine infantrymen, along with a couple thousand other fighters, had to repeat what Leonidas, 300 Spartans, and their Greek allies did in 480 B.C. against a modern foe?
First, the battlefield at Thermopylae in 480 B.C. was very friendly to defenders. The mountains pressed close to the sea, leaving only a thin gap of land through which Xerxes could press his army. This gap was further constricted by the Spartans when they repaired a low wall.
For the modern Marines, the gap could instead be narrowed with fighting holes, barbed wire, machine gun positions, and mines. Similarly, the fatal back path that Xerxes marched his "Immortals" through to doom Leonidas and his men could be blocked the same way, forcing an attacker to pay for every yard in blood.
Unfortunately for the Marines, their enemy can afford a few bloody engagements. While the Marines would boast 300 infantrymen and 6,000 other combat arms Marines, their enemy would number somewhere around 100,000.
The first thing the Marines would want to do against an enemy attack is copy the advantage that the Spartans used at Thermopylae, greater infantry range and stronger defenses. The Greek Hoplite carried a spear with slightly better range than the Immortal's swords, and Hoplite armor was constructed of bronze strong enough to protect from Persian arrows.
The Marines would need to reach back in their armories for a similar range advantage. While the M4 has an effective firing range of 500 meters, the same as the AK-74 and other common infantry weapons, the M16 has a 550-meter range against a point target, a 10 percent boost. And the Marines' body armor and defensive fortifications would give them an advantage over attackers similar to the Hoplites' bronze armor.
Unfortunately for the Marines, modern warfare isn't limited to infantry fighting infantry, and so they would need to reckon with enemy artillery and air assets.
While the U.S. faces an artillery range gap in relation to Russia and China, the Marines defending the pass could use the mountains on their west to place their guns at greater altitude. This would give their guns greater range and force the enemy to come within the envelope of the U.S. cannon to try to take out Marine artillery positions.
Air defenders would also need to position themselves up the mountains to provide an effective screen to protect their troops from enemy air attacks.
Luckily for the Marines, the Corps is one of the few military organizations that has invested heavily in short takeoff, vertical landing aircraft — meaning that Ospreys and Super Stallions can deliver supplies to the besieged Marines while F-35s and Harriers provide air support either from small, forward refueling and rearming points near the front or from a nearby ship.
All of this adds up to a Marine force enjoying much of the same successes during the early days of the battle as the Spartans did. Enemy infantry and cavalry would be forced to maneuver into a narrow gap and be cut down by Marine rifles and missiles.
Even better, their artillery could force the enemy guns to fire from afar and break up forces massing for an attack, advantages that the Spartans lacked.
But, like the Spartans before them, the Marines would eventually be overcome by their numerical limitations. Even with approximately 6,000 other Marines, the 300 infantrymen simply could not hold out forever.
Enemy assaults would make it deeper into the pass each time as engineers whittled away at the Marines' defenses and artillery crews braved American guns to get rounds onto the defenders' heads.
After a few days, the Marines would have amassed a stunning body count, possibly even as high as the 20,000 Persians credited to Leonidas and his forces, but they would be burned out of Thermopylae.
But if they could buy enough time, it's unimaginable that the Navy and Marine Corps would not be able to get follow-on forces to Greece. And, using the Marine Corps' amphibious capabilities, reinforcements could be rushed to the beaches just south of the battle.
Meanwhile, the Navy could press its jets into the fight, ensuring air superiority and providing a reprieve for the defenders.
Thanks to the mobility of America's sea services and Thermopylae's location on a coast, the battle could end much differently for the Marines standing where the Spartans once fell.