(My post on Archive) It has always been stated throughout the series that the Covenant followed the simple strategy of force in numbers. They had nearly no need for strategy if they could field an absolutely overwhelming force. Even if the odds were even and the UNSC managed to win, the costs would be horrible for them. The Covenant must have known this the further the war dragged on, considering the fact that they could replace their numbers and ships much more easily than the UNSC could. Any large scale UNSC victory on the Covenant would come as disastrous when it came back to the figures. After all, the Covenant is pulling the industrial prowess and numbers from several races (even if they are not using their full capacity for war against the UNSC), while the UNSC is at an extreme disadvantage for resources and numbers (Especially as the Outer Colonies were the first to fall to the Covenant and were the main supply of resources for the UNSC), which still leaves them severely outnumbered and with less industrial/manufacturing capacity. The Covenant extremely underestimated the UNSC thanks to their beliefs of them being vermin but, as some Elites had pointed out, they fought with honor to the end and devised impressive strategies to overcome impossible odd but The Covenant has had no real reason to change their doctrine in war as it brought back results and the Prophets could care less about losses, combined with their superior technology which made it easier for them to win. They could recieve reinforcements much faster and in bigger numbers than the UNSC could, sometimes with the force already present being able to stand up to UNSC fleets which makes Covenant reinforcements a signal to retreat before everything is lost, giving them an easy victory over an initially larger force. Covenant shield technology on ships would mean they could take multiple MAC rounds (assuming they hit their marks to begin with) before failing, depending on class, and even then a direct hit does not mean the ship is at least neutralized. Two plasma bolts could shred frigates and destroyers, with the added effect of the plasma eating through the armor, decks and vital systems. They were guided, which means essentially every plasma round would hit it's mark unless the ship that fired the round was destroyed. Also have to take into consideration the fact the UNSC had not mastered space warfare, while the Covenant have had thousands of years of experience in multiple conflicts (not counting the ones with other possible empires). Had the Insurrection never happened, the UNSC would have had no capable fleet or armament to slow down the Covenants initial attack thus shortening the war considerably. You can't really blame the UNSC for not counter attacking when they were getting beaten so bad. They simply could not spare ships for such a task when they need an entire fleet to take on a battle group of Covenant ships, or a battle group to face off a couple of ships. With the loss of the Inner Colonies, the UNSC was loosing vital shipyards and were loosing more ships than they could produce (After the fall of Reach, the Covenant could easily have bled out the UNSC in a war of attrition without the need to directly assault Earth which would have as easily meant the UNSC's defeat). They had to try and defend their resources for war efforts sake, and loosing any ships in any potential counter attack just did not seem viable for them. Not to mention as the war dragged on, actual Covenant territory was further and further away, which could mean a UNSC battle group that were to counter attack would take months or even a year or more to reach its destination, while with Covenant superior slipspace technology, they could cover that distance in days or weeks and conduct multiple attacks on different locations. IF the UNSC did counter attack, the gravity of the damage they could inflict would be absolutely minimum to the Covenant while running with the risk of loosing that entire battlegroup for a worthless attack. It wouldn't even have any effect on the Covenant's morale as it would no doubt be kept under wraps or the Covenant would simply not care at all (As I can assume happened with the neutralization of the facilities on OPERATION: PROMETHEUS and OPERATION: TORPEDO) I'm sure the UNSC saw better to keep those ships behind in order to bolster the defense. But no matter what they did, counter attack or not, the UNSC could have never won this war. On the ground, apart from obvious superior numbers, the UNSC almost always had better strategies, but facing off against plasma weaponry (which most importantly doesn't need a direct hit to cause a casualty) simply made the battles hell. Any defensive positions could be literally melted or heated enough to cause indirect casualties as well. It would just keep stacking against the UNSC. Any defenses such as minefields could be easily wiped out by waves of Grunts, as well as stocks of ammunition. Then the real fighting force of the Covenant (Elites and Brutes) should show up to fight exhausted, physically and mentally, as well as depleted ammo wise, troops. While true the UNSC forces were generally better trained there is only so much a regular human can take before breaking down. The psychological effects of loss after loss was eating away at the UNSC war effort. Of course, the higher-ups didn't really suffer from this as they were not on the frontlines, but even the most experienced of troops would eventually break down from the strain. The Covenant suffered no such thing with victory after victory, especially considering for the Elites it was considered an honor to die on the battlefield. And no, the UNSC never had a strategy to win the war. The only strategy they had was to survive it, which was most prominent with Infinity and later RED FLAG. The major difference with the UNSC-Covenant War compared to the First Contact War in Mass Effect is that the technological differences were no where near as major as they were within Halo. Even then, the war ended right when the Turians were about to mobilize their entire fleet to fight off the human force that had retaken Shanxi. The Turians would have no doubt curbstomped the Alliance had the other Council Races not stepped in and stopped them and the war would have run its course. Either way, the Alliance and Turians technology were both derived from Prothean tech each had access to. The UNSC did not have access nor time to develop on Forerunner tech as the Covenant had. Plus, the UNSC was low on their nuclear stockpile throughout the war, unlike the Alliance.