> To me it is a word whose meaning I don't really understand whose main purpose seems to justify leaders in sending people to their death at war and by men to justify murdering women/other men

You're conflating honor and valor. Honor can be derivative of valor, certainly, but they are distinct. What you're insinuating is that the military teaches honor and valor, but that'd be impossible even if they wanted to. What they do teach is a team mentality, where the safety of your fellow team mates comes before your own. I'm reminded of the story of Jason Dunham [0], citation:

For conspicuous gallantry and intrepidity at the risk of his life above and beyond the call of duty while serving as Rifle Squad Leader, 4th Platoon, Company K, Third Battalion, Seventh Marines (Reinforced), Regimental Combat Team 7, First Marine Division (Reinforced), on 14 April 2004. Corporal Dunham's squad was conducting a reconnaissance mission in the town of Karabilah, Iraq, when they heard rocket-propelled grenade and small arms fire erupt approximately two kilometers to the west. Corporal Dunham led his Combined Anti-Armor Team towards the engagement to provide fire support to their Battalion Commander's convoy, which had been ambushed as it was traveling to Camp Husaybah. As Corporal Dunham and his Marines advanced, they quickly began to receive enemy fire. Corporal Dunham ordered his squad to dismount their vehicles and led one of his fire teams on foot several blocks south of the ambushed convoy. Discovering seven Iraqi vehicles in a column attempting to depart, Corporal Dunham and his team stopped the vehicles to search them for weapons. As they approached the vehicles, an insurgent leaped out and attacked Corporal Dunham. Corporal Dunham wrestled the insurgent to the ground and in the ensuing struggle saw the insurgent release a grenade. Corporal Dunham immediately alerted his fellow Marines to the threat. Aware of the imminent danger and without hesitation, Corporal Dunham covered the grenade with his helmet and body, bearing the brunt of the explosion and shielding his Marines from the blast. In an ultimate and selfless act of bravery in which he was mortally wounded, he saved the lives of at least two fellow Marines. By his undaunted courage, intrepid fighting spirit, and unwavering devotion to duty, Corporal Dunham gallantly gave his life for his country, thereby reflecting great credit upon himself and upholding the highest traditions of the Marine Corps and the United States Naval Service

Nobody taught Jason Dunham that a kevlar, a plate carrier, and a body can stop the force of a Mills bomb. What he was taught was devotion to those he led. By living up to the standard of the USMC and USN in terms of devotion, in combination with the aforementioned properties of gallantry and intrepidity, he reflects honor on himself and by proxy the services.

Seeking honor in the service is generally a good thing - in so much as that you do the right thing even when people won't be looking; seeking valor is fairly frowned upon. Generally when I hear a story about people seeking valor you can tell the person in the story is highly annoyed, because it's considered excess risk and flies in the face of the values of the services.

[0] https://en.wikipedia.org/wiki/Jason_Dunham