War is changing. That's not too surprising, since war has always been changing. New offensive weapons appear, giving one army superiority over another. Such advances can win battles and even whole wars. New defensive weapons are developed to counter the threat, so even newer offensive weapons are then developed. The cycle never stops, really. And this has been true since the beginning of time, so it really shouldn't be surprising that it's happening in a big way once again.

An early example of how wars change was the Battle of Agincourt (which happened in 1415, during the Hundred Years' War). The British army deployed archers with longbows -- an advance the French army hadn't adopted yet. Longbows sent arrows further and with more force than the bows the French were using, so attacking knights could be killed long before they faced their counterparts on the battlefield. It was a huge upset, since the French army vastly outnumbered the British.

Advances continued. Gunpowder and cannons changed the equation that previously had seen castles as the ultimate defensive mechanisms. Cannonballs could bring down castle walls, as could sappers who dug under the walls and set off huge amounts of explosives. Later, the introduction of the machine gun and tanks radically changed the way battles were fought. Aircraft carries became crucial in World War II.

But now what might be called the "age of the missile" is giving way to the "age of the drone." Guided missiles have primarily been the mainstay of modern battles, along with tanks and aircraft carriers on the ground and sea. Launching Tomahawk missiles from hundreds of miles away from a target means very little danger to the troops who fire these missiles.

But now warfare has moved on and is writing a new chapter, in both Ukraine and Iran. Missile warfare has become a war of attrition: which side will run out first? Interceptor missiles have become extremely accurate, but they're also incredibly expensive and complex, meaning they can't be built fast enough (at least in America) to replenish the supplies a war burns up. And it's not just incoming ballistic and cruise missiles that America now defends its armed forces from, it is also a swarm of very low-cost one-way suicide drones.

Another way to put what is happening might be that the "age of the drone" is changing the equation of the "age of the forward military base." This was evidenced this weekend by the U.S. pulling all of its B-1 bombers out of a base in England and flying them all back home to America. After a very crude attempt at an attack on this base -- by five people in white vans that reportedly had barrels of gasoline within them -- America got spooked by a different sort of threat, and ordered all the bombers to fly home.

A while back, the Ukrainian military pulled off what will surely go down in military history as one of the most successful behind-enemy-lines raids in history. They pre-positioned over 100 very small suicide attack drones within ordinary-looking trucks, deep within Russia. These trucks then simultaneously drove to within a few miles of five Russian airbases (as far away as Siberia) that were the homes of the Russian long-range bomber fleet. The drones were released, and they succeeded in destroying one-third of the entire Russian bomber fleet, in one spectacular attack.

That's what America was concerned could happen in England.

The Ukrainian raid hasn't been the only example of such asymmetric warfare scoring major military victories of late, either:

Beyond Ukraine's dramatic drone mission deep inside Russia, Israel orchestrated similar attacks from inside Iran, using swarms of armed drones and explosives that had been concealed in ordinary vehicles before being unleashed to destroy missile launch sites, air defense batteries and other targets.

The covert operation, led by Israel's Mossad intelligence agency, helped cripple Iran's defenses and to clear the way for 12 days of U.S.-Israeli airstrikes in mid-2025 on Iran's nuclear weapons sites, as well as the targeted killings of nuclear scientists and members of the inner circle of Ayatollah Ali Khamenei, Iran's supreme leader.

Fleets of military aircraft and other important weapons systems worth billions of dollars are now vulnerable to a drone attack that might -- in total -- only cost in the tens of thousands of dollars.

This presents not just a tactical problem for the U.S. military but also a strategic one. America has, since World War II, operated advance military bases in dozens of countries around the world. Airfields and port facilities are maintained to keep the supply chains open and to pre-position military aircraft close to where they might be needed. One of those was situated in Bahrain -- the headquarters of the U.S. Fifth Fleet. It was attacked in the very first retaliatory attack Iran launched after the U.S. and Israel began bombing it, way back in February. Attacks have continued since then, and the acting Secretary of the Navy has even admitted that Iran "blew the hell out of Bahrain."

In response, the U.S. moved military personnel off-base, into nearby hotels. The hotels were then also targeted in subsequent attacks. So the military effectively abandoned the base and moved all the soldiers there back to the U.S. mainland. This wasn't just any naval base in the Middle East, it was where the Navy had positioned huge stockpiles of just about everything so they could resupply the U.S. warships active in the region. With Bahrain out of action, this has meant what used to be a convenient logistical resupply line has had to shift to Diego Garcia, a small island in the Indian Ocean that is thousands of miles away from the Persian Gulf. This means resupplying the fleets in the region now takes weeks longer than it used to. And the Pentagon is now considering just abandoning the Bahrain base forever.

That is a stunning victory for Iran in the midst of a war. The retreat of the B-1 bombers this weekend is another -- one that took place thousands of miles away from the battlefield. Iran quite rightly has said that any airbase that launches bombers to attack them is a valid military target.

The retreat from the Fifth Fleet headquarters in Bahrain and the retreat of the B-1 bombers have shown that the old strategy of opening bases all over the place in foreign countries might not be the clear military advantage that it used to be. Warplanes now need hardened hangers or bunkers to protect them against incoming drone attacks. Bases now need to be defended against both missile and drone attacks in ways never seen before.

Warfare is changing. And so far, all America can do to counter these new threats is to pull back and sound the retreat. That is a significant shift in geopolitical military power. My guess is that the retreat from the airfield in England isn't going to be the last time America decides to bug out from a foreign military base that was previously seen as secure.

-- Chris Weigant

Follow Chris on Twitter: @ChrisWeigant