As Sun Tzu states in Art of War, “The whole secret lies in confusing the enemy, so that he cannot fathom our real intent.”

The less your enemy knows about your movements — and the more you know about theirs — the better your chance of victory. For centuries, commanders have looked to gain the upper hand by discovering what opponents are up to before the battle begins. But what happens when this isn’t possible?

Often described as the “first modern naval engagement in history,” the Battle of the Coral Sea during World War II found American and Japanese carrier fleets facing off near Tulagi in the southern Solomon Islands, despite the fact that none of the ships ever saw each other. Here’s a look at how the battle unfolded, why it matters and what it meant for the development of new military technology.

Cracking the Code

At the end of April 1942, Japanese forces looked to expand their influence in the Coral Sea by capturing two strategic ports: Port Moresby and Tulagi. Meanwhile, the Allies had succeeded in breaking Japanese communication codes and sent out all sea and air units available under the command of Rear Admiral Frank J. Fletcher. Although they arrived at Tulagi just after the Japanese landed, the Allied forces managed to sink a destroyer along with some landing barges and minesweepers.

But the bulk of the Japanese carrier fleet remained at large and en route to Port Moresby. Unsure of their exact location, U.S. forces leveraged tools such as CXAM radar to find the Japanese ships and launch aerial attacks. And so the battle began. Four days later, 66 American warplanes had been destroyed along with the USS Lexington, an Essex-class aircraft carrier. The Allies downed 70 Japanese planes, and the damage to carriers such as the Shōkaku was so extensive that the Japanese forces abandoned their invasion of Moresby.

Changing the Game

While destroyed carriers and downed warplanes were familiar losses in World War II, most engagements were fought traditionally; ships on both sides could see each other and used onboard artillery along with aircraft to engage the enemy.

However, in the Battle of the Coral Sea, not a single shot was fired from aircraft carriers. Instead, the fighting was carried out entirely by warplanes and underpinned by radar. Instead of rushing into battle, the carriers kept their distance and relied on electronic intelligence to make strategic decisions. Leveraging both signals intelligence (SIGINT) and CXAM radar, the fleet kept tabs on their opponents and sent out aerial strikes to take down carriers and cripple operations, while the Japanese did the same. Some of the first fighters into the fray were Northrop Grumman F4F-3 Wildcats, which now have a place in the Smithsonian Museum.

And while the battle was the first of its kind, it wasn’t the last. Fighting in the Pacific theater for the remainder of World War II relied largely on this kind of electronic intelligence.

C’ing Is Receiving

Today, Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance (C4ISR) is commonplace in military engagements. The use of new military technology — such as autonomous drones, 3D imaging and AI-driven battle simulators — helps commanders see what’s coming before they commit to strategic initiatives.

The Battle of the Coral Sea helped to set the stage for this kind of reliable intelligence reconnaissance. By using the technology of their day, commanders in the Coral Sea proved that it was possible to build an understanding of enemy movements even without direct observation. While the equipment and personnel costs were high for both sides, the use of at-a-distance discovery also helped limit to the number of vessels sunk in ship-to-ship combat and instead made it possible to rely on more agile warfighters to deliver on strategic objectives.

Today, new C4ISR solutions are helping to further refine reconnaissance. For example, self-directed AI drones can now make on-the-fly decisions to discover enemy movements, while advanced imaging technologies can help to pinpoint threats no matter how they try to hide.

Put simply: Sight is no longer the standard for effective military engagements. Armed with new and evolving technologies, military forces can find strategic advantage — even when they can’t see it.