Early in the war the Swedish king Charles XII defeated Peter (against 5 times numerically superior forces) at Narva on the Baltic coast. Instead of destroying the Russian army Charles XII turned against Poland in order to expel the Saxons and to insure the election of a friendly Polish king. Meanwhile Peter had restored his army and recaptured Narva.
In 1708/9 Charles XII launched his Russian campaign from Poland. He allied himself with the Cossacks to liberate the Ukraine and advance on Moscow. The onset of winter, epidemics and Russian raids weakened the Swedish army, and Charles XII had to turn southwards.
The Swedish and Russian armies clashed in the southern Ukraine where they fought a decisive battle at Poltava (1709). Peter personally prepared the battle: he transformed the battlefield by works of his engineers, who were ordered to erect redoubts in the paths of the Swedish troops to break their combat order, and to split them into little groups. The battle ended in total Swedish defeat and the wounded Swedish king had to escape to Turkey.
This was the first foreign catastrophe in Russia of modern times (as later by Napoleon and Hitler). Peter's victory at Poltava was followed by Russian attacks on the Swedish possessions along the Baltic Sea and Hannoveran and Prussian declaration of War.
When Charles XII came back to Sweden he established at military dictatorship and attacked Norway. But when he died in the siege of Fredrikshald (1718) his men were ordered to return to Sweden. In the Peace of Nystad, 1721, Sweden had to give up most of their conquered land in the last 100 years (and some more). With the result that Russia supplanted Sweden as the major power in the Baltic area and Prussia in northern Germany.
Prussia came under the sway of the French during the Napoleonic Wars. But later under Bismarck went on to conquer virtually all German speaking lands including the neutral Northern German States including Hanover, and the Southern German State of Bravaria. Exceptions being Germanic populations within Austro-Hungary, Switzerland and small pockets deep within Russia. He is quoted as saying "The issues of the day will not be settled by speeches... but by blood and iron." Prussia later went on to become the German Empire. After the Germans lost World War II all eastern Germany was occupied by the Soviets. They expelled all German speaking people from Poland, the Czech-German Sudetenlands, East Prussia and Silesia (a province rich in Iron Ore) deporting them to virgin lands in Soviet Central Asia. This was done without the approval of France, Britain or the United States. Half of the former Prussian territory went to Poland, the other half became Kaliningrad (previously known as Koenigsberg) a forward Russian naval base still within the Russian federation today and re-populated with ethnic Russians. The Baltic states also have a sizeable ethnic Russian population now as well. The state of Prussia was legally abolished in 1947 by the Allied Control Council.
Poland lost its independence being divided between Russia, Prussia and Austro-Hungary. After the Russian Revolution Russia pulled out of the Great War allowing some Polish territory to become independent at the request of the Germans to make a safer boarder. When the Germans and Austro-Hungarians lost the Great War the part of Poland that was within their territories also became independent and Poland was even granted a 'free port' at Danzig / G'dansk giving her access to the sea. Independence did not last long though as Nazi Germany and the Soviet Union made the secret Molotov-Ribbentrop pact to divide Poland and much of eastern Europe between them. Faced with a duel attack from the West and East and armed with outdated equipment the Polish army was soon overcome. Although Britain and French declared War on Germany they did not do any active fighting. The period of the War was called the foony War. Until the invasion of Denmark, Norway, and France.
The Poles suffered terribly during the Second World War with one in five being killing. Many Poles were deported to Soviet Gulags but when Russia was in turn attacked by Germany were allowed to form a Polish Communist Army to fight alongside the Russians. A few poles also escaped to Britain to become fighter pilots or fight in North Africa. After the War the Soviets installed a Communist government and gave Poland vast stretches of former German territory while at the same time adding about a third of former Polish territory to the Soviet Union and expelling ethnic Poles. Before the war 10% of Poland was Jewish (as opposed to 1% in Germany), after the population was only a few hundred.
Sweden allied with Britain, Austria and Russia during the Napoleonic Wars, and then later adopted a very pragmatic and wise policy of neutrality. Being isolated by sea, thick forests and a hostile climate few countries judged it worth the expense and trouble to conquer her, especially with so many other enemies around. Her policy of neutrality increased this tendency as did her limited resources. Also Finland acted as a buffer against Russia. During the Second World War Sweden provided a major source of Iron Ore for Nazi Germany. Although Sweden wasn't invaded judging it wiser to yield to overwhelming force. Both Denmark and Norway were invaded principally to protect the Ore supply route which ending in a railway at a Norwegian port. Britain had garrisoned Norway to prevent this, but this just incited the Germans. The Germans of course also wanted to have more naval bases on the North Sea.
Hanover was an independent state in north-western Germany, and a electorate of the Holy Roman Empire (famously said to be neither Holy, Roman or Empire), which was a very loose confederation of Germanic states which occasionally aided each other in War and Trade. Each state got one or more votes in its council. Hanover also had access to the North Sea and was officially called Brunswick-Lüneburg. In 1714 George Louis, elector of Hanover, became King George I of Great Britain, even though he could speak no English. For nearly 125 years thereafter, both Hanover and Great Britain were ruled by the same sovereign until the French invaded. Great Britain was not called Great to reflect its growing power as most people think but to distinguish it from Brittany in France, one being Greater Britain and the other Lesser Britain. Hanover was established as a kingdom in 1815 by the Congress of Vienna at the end of the Napoleonic Wars. This may in part account for why so many settlers of German decent went to the British colonies and served as Hessian Mercenaries. After the Seven Week's War (1866), Hanover was made a province of Prussia. With the formal liquidation of the state of Prussia in 1946 it became part of the new state of Lower Saxony.