This is my second (technically third) post on the subject of how the UNSC could have fought the Covenant more effectively. We already discussed improving UNSC defenses against Covenant weapons, including the possibility of developing ERA shielding earlier in the war. But my second thought is: why does the UNSC have to fight the Covenant head-on in the first place?
EDIT: I'm NOT talking about using Prowlers as combat ships. I'm proposing an entirely new class of large UNSC warships designed around stealth from the beginning. They would use technology derived from Prowler stealth systems, but be much larger, heavily armed, and capable of maintaining stealth continuously.
If you think a large ship couldn't have a sufficiently small sensor signature, consider the B-2 and B-52. The B-2 is a large aircraft, yet its radar cross-section is dramatically smaller than that of the B-52. So I don't see why the UNSC couldn't theoretically build a large warship with a much smaller sensor signature than a conventional cruiser or destroyer.
The ship wouldn't need to be as stealthy as a Prowler. It just needs to be stealthy enough to get into position without being detected.
For example, imagine a Covenant fleet entering a system while one of these ships is hiding behind a moon, using the moon as physical cover from optical and other line-of-sight sensors. An isolated Covenant ship enters the area, the stealth ship comes out, unloads its weapons, destroys the target, and immediately jumps into slipspace.
The real purpose would be to operate behind the front lines and deep inside Covenant-controlled territory, hunting isolated ships, transports, supply lines, repair facilities, communications infrastructure, and other high-value targets.
Then comes the deception part.
Yes, I know space is fucking enormous. I'm not suggesting putting a probe every few kilometers across the galaxy.
The UNSC had 28 years of war. Earth wasn't found on day one. Humanity had hundreds of colonies, shipping routes, military installations, logistical corridors, and entire regions of space that the Covenant had to search and move through.
The UNSC could deploy huge numbers of relatively cheap probes throughout strategically important areas, or use them to make the Covenant think that certain areas are strategically important. These probes could generate detectable signatures, including Cherenkov radiation associated with slipspace activity. Human colonies and military installations could also create false signatures mimicking UNSC ships or fleets.
The UNSC would know which probes were real, which were fake, and when they were supposed to activate through identification systems and timers. The Covenant wouldn't.
That creates a massive intelligence problem.
The Covenant wouldn't know how many UNSC ships actually exist, which contacts are real, which are probes, which are false signatures, or which might be actual stealth ships.
That forces the Covenant to spread its forces across a much larger area while investigating potential threats.
And that's where the wolfpacks come in.
One wolfpack attacks a logistics group. Another hits a convoy. Another destroys a repair facility. Another attacks an isolated group of warships. Then they all disappear before the Covenant can respond.
This is where the WWII wolfpack comparison comes in. The objective isn't necessarily to destroy the enemy's entire navy. It's to destroy its logistics.
If you continuously attack supply lines, repair facilities, transports, communications, and isolated ships, you make maintaining the war increasingly expensive and difficult.
The UNSC doesn't need to win every engagement. It needs to make the Covenant fight a war where every convoy could be attacked, every sensor contact could be fake, and every logistical route could potentially be a kill zone.
Combine the Cole Protocol, massive numbers of deceptive probes and ship signatures, and heavily armed stealth wolfpacks operating deep behind the front lines, and you could turn Covenant-controlled territory into an interstellar jungle.