Hey M8 don't let it get you down....I remember my total frustrations with the STW battle tutorial where you just had one unit of archers to take out one unit of spears....I almost through the disk out the window!!!
I will give you a couple of ideas and I am sure some more folks will jump on the topic as well...
1) This is a problem when you are trying to move the entire army as a unit and you have slower moving footsoldiers in the front... When I am the attacker I will use this method, but only in the very beginning stage of the battle, as the terrain changes and the opposition moves, I have to think of the easiest way for my troops to get to where they will have the best advantage.. Try painting your spear units to a position and then while hitting the space bar, paint in your next line. I find that painting them into a formation in smaller groups is much more efficient than trying to get the whole army to move as a unit. I think that this will help with #2 as well(the alt right click really only works for one unit at a time)... find pairings that work together for you...Like in your battle above I would place the archers in front(probably not grouped) having them in "skirmish" (unless I really want to hold my ground and fire till you see the whites of their eyes by using "hold position"), Then I would make two groups of 2Viking units each just behind them. Then I would have the cavs in back and have them ready for flanking or cleanup.
3) The formations are good only to a point...I enjoy experimenting with the differant formations and seeing how I can attack or defend using the way they start you off....But this is really only just the beginning, after that you have to use your head and do things that make sense to YOU.
4) Archers are great for many things...Try to keep the high ground...They do so much better when they are above their targets..keep them in lines no more than 3 deep preferably 2 as this will give them a better view of their targets....I don't like to leave them in the "fire at will" position as they tend to shoot when the enemy is still really too far off....wait till the arrow turns green for a while before targeting your enemy....then move in the archers protection as they get closer and closer...this is when I switch the archers to "hold position" so they won't keep running back...if they are protected, there is no sense in them moving back...hold the line and instill fear in the enemy...
5) No not all battles end up this way...stay organised and keep your mind working...remember to use flanking moves and use each unit for what they are best at.
6) practice...practice..practice

There are many keys to winning....High Ground!!!!!is the biggest one...If the defending army is on a hill attack him from above, even if it means marching your army a long way. I have had lots of fun marching my armies to high ground experimenting with formations and lines, trying to make them move like a real army would move...then when I aproach the hill I use the paint method to make the formation that I think would work best.....
Don't give up m8...keep trying and just try to enjoy....If you lose...think about what the enemy did and try to learn from the ai...


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Watashiwa Yagyu Jubei desu! Ganbate!