On October 25, 1415, King Henry V of England faced the grim prospect of a calamitous end to an otherwise successful and lucrative campaign in France. He was overlong in the field and over-extended from his strong hold in Normandy. His 1,500 men-at-arms were caught near Agincourt with a 5:1 disadvantage in blades to a determined French enemy. King Henry faced the prospect of battle with wave after wave of superior numbers who should — by any estimation — have overpowered the English. But Henry had an ace in the hole.

Assembling his knights, Henry laid out a battle plan placing his men-at-arms in a strong line, protected from cavalry by pickets, and arranged to ensure the maximum effect of his Welsh longbowmen. Henry knew that the temptation to break ranks would be intense. Within earshot of French revelries before what they presumed would be an easy victory, the English knights heard the Dauphin’s nobles drinking, gambling and fighting to be assigned a place in the first battalion. The French hoped to snatch an English noble who could be ransomed per the code of chivalric combat. The English knights likewise would have harbored a desire to do the same, but Henry was adamant that breaking the line would be punishable by death either during or after the battle.

Henry knew his line must hold or the archers would be slaughtered, and it was the archers who made the 300 meters between the English and French lines a killing field. Henry intended to repeat the tactics of Crécy, an English longbow victory from a century before, using archers to thin and disrupt the assaulting forces. Arrows would slow and mangle the French advance and allow for a local English advantage at the point of contact despite the overall asymmetric advantage of the French.

The value of archers requires some explanation. The Welsh had a marginal quantifiable advantage due the to natural “composite technology” of their self-ewe longbows. While the French crossbowmen could fire a bolt with more force — penetrating steel armor — longbowmen could fire 2-3 arrows to each of a crossbomen’s bolts. With 7,000 archers divided into two tightly packed lines, the English were able to rain tens of thousands of arrows down on French knights who were bottle-necked into a single-axis approach.

Archers were limited in their ability to engage; maximum high-angle range was around 300m and minimum range was direct fire at the fringe of a melee. Archers are no match for cavalry — but Henry used wooded terrain to make a cavalry flank attack on archers impossible while picket lines before them broke up charges. Likewise, archers were no match for men-at-arms, but it was safer for a Frenchman to engage in the melee or press of main battle than to charge the archers and expose his flank to the English line or his chest to a lethal barrage of direct fire. Together, the archers thinned the “swarm” of attacking forces by bringing rapid engagement capability to bear, giving the defended knights better odds against fractured assaults. The archers at Agincourt also did notable service as skirmishers, but their value was ensuring that English knights enjoyed a local, tactical, advantage despite a strategic disadvantage.

There is a lesson from Agincourt for today’s Airmen, specifically vis-à-vis the A-10. There is a difference in forces designed to offensively interdict and achieve superiority (the comparison’s to light and heavy cavalry are obvious), and those whose attack capability provide a distinctly defensive advantage.

Consider that at Agincourt, the French blocked the English escape to Normandy and had thus imposed a battle at a time and location of their choosing. Further, Henry lacked the forces to conduct an offensive breakout. He needed to fight just to hold his ground and win a victory on the defense. Now consider a US Navy aircraft carrier penned inside the Arabian Gulf. If the straights of Hormuz were mined shut, the carrier would have to fight in place, likely prioritizing defensive maneuvers above aircraft launch and recovery operations. The threat in that case would be Iranian attack boats that can close rapidly and torpedo or ram the carrier. The loss of a US Capital ship itself would be an unfathomable strategic loss, potentially made even worse by the specter of Iranians capturing US sailors as they abandon a sinking flattop.

Much like the Henry’s knights, the carrier would need to be able to bring in a fury of fires from the air since the period of the attacking swarm’s vulnerability is brief. If air attacks are too slow, attack boats could close with the carrier to the point where air delivered fires would be a danger to friendly forces. Much like the archer, the value of air support airpower is the ability to achieve as many kills as possible between the time an adversary leaves protection and when they close to contact with a defended force. Nothing is designed to bring a fury of fires like the A-10. It was designed for this exact kind of battle — buying time and attriting swarms of Soviet tanks as they poured through the Fulda Gap so the defended land forces would have better odds of holding Western Germany. It was designed to take damage because this mission involves being in the line of fire — the vantage from which maximum firepower can be returned.

There are many other missions the A-10 can do, and there are many other planes that can do some of what the A-10 does well, but many pundits have lost the recognition that sometimes our forces will need to win defensive victories. Sometimes it is more important to be able to expend airpower to ensure the defense of a strategic asset than to have airpower designed for exceptional offensive capabilities. Political realities mean we will not always be able to pick the time and place of our battles, and when the adversary is able to marshal in plain sight and close proximity to our forces (as Iranian attack boats are), an attack aircraft with rapid engagement capacity is a decisive advantage. Nothing could defend Western Europe from Soviet tanks like the A-10. Nothing has defensed our troops under fire on the ground like the A-10. It is likely that nothing could defend a carrier in the Arabian Gulf like the A-10. There are times when we cannot accept being simply “OK” at a mission, and defense of a strategic vulnerability is one of those times.

Swarms are a unique threat, whether they are tanks, Taliban fighters surging over Hesco barriers, or Iranian attack boats. When the enemy is able to take offensive initiative, exposed to fire only during a brief movement to contact, something with the firepower, multiple target engagement capacity, and re-attack speed of an A-10 will excel. Whether that is sufficient to convince people to keep the A-10, or to invest in an OA-X, remains to be seen.

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