Are you either one side or the other of a river? Do you ever measure distance and be partially across a river?
I believe you are either on one side or the other unless it is dried up or ankle deep when it does not affect movement and you can move through it normally. To cross a chest high or waist high river you have to start with your front touching the bank on your side, then pass a CMT and end your move with your rear touching the opposite bank.
Note also that you can not shoot across a river with infantry that requires a CMT to cross. River has to be at least 2 MU wide so is more than shooting range, and reformed do not shoot over rivers either. Their inherent skirmishers stay with their parent unit so no shooting across the river. Also Cavalry does not reduce shooting dice against infantry on the opposite side of the river if a CMT is required to cross. Their harassing companies stay with their parent unit on their side of the river as well.
Rules page79 "cavalry cannot assault a defended river unless ankle deep or dried up"
Looking at rivers and fords it looks like you can assault across them in tactical but you will need to pass a CMT to do so and would end up "in the river" during combat. Note that page 70 Rivers and streams says in shoulder high water defender counts as defending obstacle, attacker fights as 2 levels of cohesion lower, so disordered can't fight, they would count as broken as the rules stand. Personally I would go with fight with half dice myself on that one, it covers disordered attackers better and is more or less what is implied. However in the next section on page 79 bridges and fords it says: if the water is shoulder high the assaulting unit also fights at 1 cohesion level lower.
You can see the discrepancy on the same page here.
page 62 "retiring units stop after crossing obstacle"
You can retire across an obstacle , a river is an obstacle , it follows you can evade across a river?
Once again if it requires a CMT to cross I would say no. There is no occasion listed in the rules for taking a CMT while evading. My guess is you stop at the river on the same side as you started on. If ankle deep it still counts as an obstacle so then I guess they would stop after crossing to the opposite bank.
situations cavalry charge skirmishers with their backs to a river (waist high)
can the skirmishers evade across the river?
do they stop after crossing the river (retirements stop after crossing an obstacle , the river is an obstacle?)
Once again I don't think you can evade across a river that requires a CMT to cross so you would stop when you get to the river bank. To normally cross or assault across a river you have to start touching the river bank on your own side, then next turn take the CMT to cross or assault across it. Even if the evaders start touching the river bank it takes a full move to cross and in an assault you don't have that kind of time happening. You are not going to get across before the cavalry arrives.
Once again ankle deep does not stop movement so you would evade across to the opposite bank then stop as it is an obstacle. At least you get the obstacle defence bonuses.
have far do the chargers go? normal charge move (just measured ignoring the river?
If CMT required to cross: Chargers would make their normal charge move or stop at the point of contact or at the rivers edge whichever case it may be. They can't cross or enter the river if a CMT is required, I assume they did not start touching the river so they would stop at the river on their starting side, or in the case of an evade when they contact the evaders who could not evade across the river either. Bad place for infantry.
If ankle deep or dried up: Cavalry will make the full charge move or stop when they contact their target which ever comes first. If they contact the cav will stop in the river touching the opposite bank that is being defended by the evaders who count as defending an obstacle.
Cavalry charge cavalry across a river
Can you charge your full distance ignoring river?
No you do not. Your target has to be on the opposite river bank, unless the river is ankle deep or dried up in which case it does not affect movement. If you need a CMT to cross a river you start touching your bank and end touching the opposite bank, or end in the river fighting whoever is on the opposite bank.
DO you need a CMT? (you dont need a CMT to assault buildings but you do to enter)
You need to pass a CMT to assault across a bridge or river which is chest or shoulder high.
Do cavalry counter charge across a river?
I think it depends on the river depth. For chest or shoulder depth they have to be on the opposite river bank and would wait for the assaulting unit to get out of the river. Once again it would require a CMT to enter the river in the first place.
For dried up or ankle deep, the river is the same as open ground so I would think normal rules would apply and a counter charge would likely be in order.
Hope that helps, now where did I leave that mask and snorkel??...