Warcraft's unit limitation is 12 not 20
havent tried the map yet but i will later
and will give a short review after playing

Edit:
The game can be finished with no strategy at all. The game was rather slow in the beginning in classic mode. the kills needed for each units is too high, it is nearly impossible for the same unit to kill 50 enemy units. .I could still be improved work hard for this map to be better than other risk maps..
Terrain is plain normal but well made, just not that appealing.
Suggestions:
-There should be 1 race for each players (can be a mode)
-Some towns have specialties like having to train units faster, larger income and others
-There should be heroes or hero-like units that are stronger than normal troops
-aside from a mass attack option there should be a make squad function that can hold up to 20 or something
-A different variety of towers
-A limit to number of units, maybe each town can provide a limited number of troops or all together
-Terrain advantages (ex. High cliffs + range units= more damage) and for each unit/race/class
-Higher/faster income (maybe a mode)
-More different types of units
-Racial advantages i guess.....
-Air transport
-King/Queen/Ruler (will give bonus to all units but when it dies it takes a lot of time to make another one and all units get weaker)
thats pretty much it good luck with your map and i might play future versions
3/5