Swamps, rocks and cliffs determine major avenues of approach on this map. This map, with sparse protection and no buildings, gives the combat advantage to artillery. Concentrate your attacks along the path of your main advance, while conducting delaying and defensive actions along the rest of your front lines.
Karelia is a notorious SPG favored map; plenty of open terrain, huge lanes for sniping, and the famous donut makes this map a very tactical one. Proper division of forces and knowing the correct areas to shoot from are some key ways to boost your chances for a win. Above all else though is the need to know the areas that artillery can hit and those that you are safe from.
One of the three major routes if the Northern area, known as the Rocks. The cover here is fairly decent, compared to the rest of the map, but only consists of a few outcroppings of rocks. It will become key to have heavies play peek-a-poo here while mediums proceed to flank behind the enemy and engage their rear armor. Direct head to head stalemates can often be broken here by accurate SPG fire and a well placed TD. Primarily a decent chunk of the army should head this way, mostly heavies and mediums are preferred over TDs, while a single artillery dedicated to this area will be able to turn the tide is things grind to a halt. Remembering to hug the rocks and squeeze into any area possible will serve the player well.
On the Southern side of the map lays the area known as the donut, the most popular attack route on the map. The donut can be fairly complex even if it looks simplistic and straight forward. The main objective is always to rear the top of the of the donut, pushing back the enemy forces and being able to shoot down into the rocky outcroppings, as well as being able to cross board snipe. Any tank with a decent speed should make a best attempt to capture the donut so long as they are confident that they can make it. Once committed to this, it is very difficult to back-track if spotted by enemy forces and so one must weigh out if they believe they can make it safely or not. Alternatively, there rocky outcroppings do offer protection for forces fighting head on and can be utilized quite well my mediums and TDs. Heavies and other TDs may find success in the corners labeled with stars. These areas usually have bushes to provide concealment as well as having room with which to play peek-a-boo back and forth. This area can quickly become bogged down and require luck, boldness, or well placed SPG rounds to break-through.
The final path, the center swamp, is a dangerous gambit to say the least. The only tanks that should ever consider this route with any sanity are scouts/light tanks, and fast mediums. The issue with this area is that the terrain, the swamp, will slow down any tanks traveling through the area, except directly on the center road. While shrubs offer concealment, only a few sparse rocky outcroppings offer any protection from players on base defense. Hugging the sides of either side of the swamp may prove more beneficial than the direct center road for sneaky assaults, but a quick scout can some times successfully traverse the road at high speeds and make a direct attack at enemy artillery positions in the rear and sides of the base. SPGs can usually find their place along the back of the base, or along either of the edges along their deployment area, usually being able to cover their one dedicated lane, along with mild support to the others. Karelia is their map, and hiding spots are plenty, but direct lines for fire often come with exploration to new and creative positions.
Effectively plan around this analysis, use the route to your advantage to best take on what tanks to expect in each area, and always support where areas are lightly defended but be ready to reenforce as needed. With a good platoon at your side, and now knowing this map better, you may just be able to sample the almighty donut.