How to war on land?

Hello. This is my first post on the forum.
I have looked at strategies on here before but I decided it was about time that I finally asked for help.


That bit of information may be important to you if you are to help me.
So anyway my problem is with land warfare. I am very good at Civ after over 250 hours of online play and even more offline since I got the game in July of 2014. I am very good at empire building (particularly tradition), wonder spamming and generating a lot of science, culture, gold, faith and happiness. I am the scourge of the seas in the group of people I play with, I am a genius at naval warfare and have only ever lost naval battle which was due to my reliance on ship of the line and the fact that my iron supplier joined the war against me which rendered the ships useless. I almost always win domination of my enemies settle coastal cities (early game galeass spam as Ottomans is a brilliant strategy, or frigates if the game drags on). I also am very good at fooling everybody in the game and backstabbing them without them suspecting a thing. I'm able to predict every movement in the worlds congress and have every resolution I want passed or failed. All in all I have won nearly every civ game with my friends, and I am considered to be the biggest threat.

However, I absolutely suck at land warfare.

One guy I play with is my biggest ally in half the games and my worst enemy in the other half. He is almost as good as me at empire building and science, but when he fails early game he basically gives up and recludes into the background and stays low, in these cases I win, in these cases he tends to also drain from me and become my ally which allows me to backstab him easily. If he equals me early game though, we are always at each other's throats unless there is another powerful alliance in the game. But if we are at war and on the same continent he always wins. He is the only person apart from me to have won a game in our friend group of 8 or 9 people.
He is very good at land warfare whereas I am terrible. I am good at grand strategy as in knowing where to attack from and how to surprise an enemy, but I have no clue about troop formation and how to come back when my army is diminished. I really need a basic how to guide on how to kill someone militarily. It would be much appreciated if someone could help me.
(This guy has only ever lost one land battle, the same way I've only lost one naval battle)

This is pretty much all you need. A very comprehensive guide to the whole combat system, explaining the role of units, how to use them together etc.

Thank you so much!

If it's an early war mass chariots and composites, If Medieval then rush and use xbows and later add knights when you get the tech. Ranged units reign supreme in civ 5.

In renaissance muskets own with xbows behind them. If you are planning on war in the mid game then rush artillery and use oxford on dynamite. Artillery are a game winner every time. At that point in the game your army should be mainly just artillery and cavalry with some melee to tank in front of the artillery.

In general you want to get surrounds on the enemy. Move to the side to flank with some units as opposed to all forward. If you can get some units on the edge of the battle and come from the side you will have an advantage.

When attacking a city be sure that as many units as possible enter its range of attack on the same turn. Never ever attack single file.