HISTORY OF A2/AD

Written records of anti-access warfare strategies date back to 480 BC, when the independent city-states of Greece were menaced by the Persian emperor Xerxes and the largest armed force ever assembled at that time. According to the historian Herodotus, Xerxes’ forces included 1.7 million troops and 1,327 warships (although the number of troops was, in all likelihood, much smaller; the larger number may have included warriors as well as camp followers). In contrast, the Greek city-states each had only a few thousand defenders and had rarely before been united.

The weaker Greek city-states were able to defeat Xerxes and his great army by pursuing a strategy of anti-access. The Greek islands provided natural barriers and chokepoints that the Greeks used to their advantage to destroy or cut off critical supply and logistic lines. By preventing the necessary supply ships from reaching the soldiers ashore, the Greeks turned Xerxes’ strength into a weakness: His army was too big to live off the land and could not survive without shipments of grain, which could only be brought by sea. The Spartan rulers convincingly bluffed that more Greek forces were on the way and that Xerxes had limited time to save himself and his troops before they would be cut down by the approaching Greek warriors. Xerxes retreated to Asia and left behind a contingent of 20,000 troops, which suffered from starvation and desertion, and was eventually destroyed by the Greek warriors.

The largest army the world had ever known at that point in history was denied access by a much smaller force, and the mighty Xerxes forfeited his goal of conquering all of Greece. Instead of achieving victory, he was forced to retreat. In this case, the power of the anti-access strategy was that it allowed the weaker force to prevent the stronger force from bringing its resources to bear in the theater of operations; in other words, it neutralized the superior force and then waited for time, attrition, and/or extrinsic events to shake the determination of the attacker or change the cost–benefit calculation. Sun Tzu said it is better to never fight the enemy at all, but rather to be victorious without a battle. Anti-access and area denial, or A2/AD, strategies can defeat an enemy with minimal fighting.