http://www.benning.army.mil/Armor/Histo ... Battle.pdf
"Armor in battle" published by US army armor school introduce about armored battle during Korean war. Here, they introduced about Korean terrain in page 180:
a. The terrain in Korea is mountainous with numerous valleys, a situation which does not lend itself to
armored warfare as known in Africa and Europe. Armored operations are further channelized at this time of
year by rice paddies. These rice paddies utilize every piece of ground which can be leveled and flooded with
water. While they do offer a hazard to vehicles, they generally have a fairly firm bottom. The soft bottom ride
paddies when found are generally along the river banks. Armored personnel advised that light tanks M-24 and
personnel carriers could negotiate rice paddies about 80% of the time when the rice paddies are wet and
believed that when they are drained, which will start in September, it will permit freedom of maneuver of full
track vehicles. In negotiating the wet rice paddies with full track vehicles, turning must be minimized and drop
off should be downhill from one rice paddy to the other rather than attempting to climb from one rice paddy to
the other. Foot troops do operate through the rice paddies, but it is not done when commanding ground is
nearby.
b. The Soviet type tank T-34, while generally reported operating on the roads, did go into wet rice paddies
at times, operate along railroads, in stream beds and on the brows of hills. While Armor appears to be
channelized it can operate and have some maneuver. Valleys in some cases offered one road, one railroad, one
stream bed (wet or dry) and two hill brows, one on each side, plus the risky rice paddies. The northern part of
Korea becomes cold in the winter time with the possibility of freezing of the ground and water ways which will
facilitate the operation of Armor.
c. There are a few non-fordable rivers in Korea that will require bridging, but most of the other rivers can
be forded with caution.
d. Roads are practically all dirt or macadam (black top usually found close to the cities); the width will
vary from a trail 10 feet wide to a 22-24 foot width for the best dirt roads. Engineers state that the roads, while
rough have a fairly good crushed rock base. The roads are built on fills in the flat country and it is generally
eight to 15 feet from the road surface to the flat land. In many places small trees (four to six inches diameter)
line the road on both sides, preventing entire freedom of gun move for tanks. The bridges across the gullies will
hold about 10 to 15 tons. The Koreans in the south have built tank bypasses. In many cases the bypasses cut
from the road are too narrow and will have to be reworked; also many of the dips on the bypasses will have to
be filled with solid material in order to give a firm footing if many track vehicles use the bypass. Dispersal
areas for Armored equipment will require utilizing villages and rice paddies. Tank dozers can be utilized very
profitably and were listed as a “must” by all commanders. It was further agreed that matting should be carried
in some quantities to help in field expedients.
e. Buildings and walls in villages were of flimsy combination of mud and small rock construction, except
roofs, which were thatch with rice straw. Buildings and walls in better sections of cities were of light wood
construction except roofs which were tile construction. There were few permanent type structures as we know
them. Practically all walls and buildings can be breached by gun fire. A tank can easily go through the
buildings with no caution about cellars or basements but with some caution as to fire hazards. Villages and
generally the cities can be set on fire easily.
Though this descriptions are based on experience from 1950 Korean war, characteristics of rice paddy are still the same. I highlighted the important part here. Unlike my initial expectation, report mentioned that rice paddies have mostly firm bottom ground, only paddies near river bank might have soft bottom. US and USSR tanks have no problem to maneuver on the wet paddy, even light tanks were able to maneuver on wet paddy field without any problem for 80% of attempt. But frequent turn, and going uphill from wet paddy to go out can be an issue so.
Currently, this game's bog / stream tile has 20 vehicle maneuverability, while fields have 80, roads have 90+, and long grass, brush, vineyard has 70. I think 20 is too harsh, but 70 is too generous for paddy. For paddy it should have following option IMO:
1) Should have 40~50 vehicle maneuverability during wet season (May ~ August), and 70~80 vehicle maneuverability during dry season (September ~ April) Is this can be achieved via map's default.xml? May I ask now can I do this?
2) Should have a bit more chance to immobilize tracked vehicles when they attempt turn, or when they go uphill on the paddy tile. (Is this possible?)
This way, uniqueness of rice paddy can be fully described in this game.
Or, do you have any better alternatives for paddy?

