Move out horse cavalry first to get a feel for the area, 
then send up conscripts, other infantry, armor, and artillery. 
There will be a major bottleneck if you don't juggle your units 
just right to keep the roads clear. This can paralyze you long 
enough to cost you the battle. Speed is crucial. 
 
Once you've pushed north a bit on both flanks, both battle 
groups will instantly run smack into the solid wall of the 
Mannerheim line. You're only going to pierce this at the two 
cities, avoiding the center. Use conscripts to draw fire from 
the pill boxes, then pour artillery on them and start to break 
down the cities' defenses with stronger infantry and armor. 
Each city has a 37mm anti-tank piece, which you'll need to 
clear with artillery and infantry, so your tanks can maneuver 
in peace. Take out enemy artillery as quickly as possible, 
and keep your own artillery fire up. It should only take a 
few turns to liberate both cities. You can use your 
paratroopers to either harry units from behind the Mannerheim 
line, or save them for the attack on Sortevala. 

Keep moving up the coast with your cruisers, laying fire on 
the forts while staying out of range as much as possible. 
Watch out for the two subs patrolling this area: they're 
not much, but they can take a bite out of you before they 
go down. You're going to want to bring these ships into 
the channel (which will draw shore fire), so you can begin 
to pound Viipuri.