Can or cannot 4 ships in river prevent crossing?

[Wheat]

I've seen it stated that 4 combat ships prohibit land units crossing rivers. Well I had the river interdicted with 4 gunboats all along the river but Forrest still crossed with 8000 men, supply wagons etc. I know he has an evasion bonus, but come on. Rosecrans and another force were after him (even started the turn in same region of Meade, KY) but now I get to chase him all over, completely clueless which way he goes and with his movement bonus.....

So the ships are useless to stop this? He went from Meade to Harrison, IN right through the ships that were ALREADY in place.

[grimjaw]

Someone will correct me if my memory is failing me, but I think the rule is that is significantly lowers the chance of a crossing but doesn't absolutely prevent it. I don't know how much the evasion factor comes into play during the river-crossing equation.

[minipol]

I think grimjaw is correct. However I can't seem to find in the wiki that there is still a chance troops can cross.
It does state troops can cross if there is more then 1 region to cross the river, or if there is an enemy ship in the region.

[seathom]

If I'm not mistaken, 4 naval elements results in a 90% chance to block enemy movement. Adding additional naval elements will not increase the blocking ability. Therefore there will always be a 10% chance of the forces crossing.

[DrPostman]

There is always still a chance, no matter how small, that they can get through.
Think of it as Forest being very lucky and getting conditions just right to cross
without notice. It happened more than you might think.

[Cromagnonman]

I thought the blocking ships had to be in attack posture and defensive...

[grimjaw]

I thought the blocking ships had to be in attack posture and defensive...

I think they have to be in something other than passive (green) mode.

[Gray Fox]

From the AGEOD Wiki:

http://www.ageod.net/agewiki/Bombard_and_Blockade

"bloValueBySU_LinkCut = 20 // Perc chance for each combat ship (cumulative) that a transition link over water is cut between 2 land regions.
bloMaxPerc_LinkCut = 90 // max chance to have the link cut.
bloMinSUForLinkCut = 4 // Min nb of elements in offensive posture in a water region to cut the transition link between 2 adjacents land regions"

So it seems that 5 ships would be necessary for at least 90% chance to block (5 x 20% = 100% then maxed to 90%) and they would need to be in offensive mode.

[Captain_Orso]

If you look in GameLogic.opt you will find:

bloValueBySU_LinkCut = 23 // Perc chance for each combat ship (cumulative) that a transition link over water is cut between 2 land regions.