Over land, sea, and air
1955 A.D.: The standing protocols of Operation Justicar, having defended Graz since the start of the war, continue to prove exceedingly effective. Not only do they hold the city, but they inflict crippling losses on every Greek force sent to take it.
On the Eastern front, the Norse army seizes control of Tunsberg Fields, forcing the Greeks to retreat West to Salzburg and leaving Mytilene and Elis open to attack. It is also discovered that Greece has constructed a small military base called Herakleia in the Austrian Alps.
Seems like one of Greece's favorite, annoying, total douche moves is to just plop cities down wherever there's room near your borders. The town might as well be named "trollface.jpg". It's irritating and inefficient and dumb and I hate it. Whatever, I'll deal with it later.
1956 A.D.: The Norse perfect radar, and begin constructing a more advanced air force.
Awww yeah. Greece is still using World War I-era biplanes and triplanes. Now that I have for real fighters and bombers, his little hobby shop toys don't stand a chance. Next stop: Nuclear Fission, the last piece of the puzzle needed to build atomic bombs and nuclear reactors.
Summer, 1957 A.D.: A great statue of the founder of the Awesomeness Religion is built in Sigtuna.
With Cristo Redentor, I now officially have more world wonders than anyone else on the map. It will help me earn policies faster, which is going to be crucial at this stage.
To the North, the Greek navy closes in on Helsinki, having sailed around the Southern horn of the continent for a surprise attack. With their Northern ports blockaded, Greece offers a peace treaty that would require the cession of all of Denmark, as well as the city of Graz. The Norsemen refuse.
Greece has actual, metal battleships now, and I don't have much of anything in that area to defend. I'll need to drop some gold to get some submarines out immediately, defeating the Greek navy the same way I did the Danish one.