The Russo-Turkish War was the last hit for the struggling Arabian Empire. The war cut off all trade routs in Middle East and once mighty empire collapsed into several city states. However, after the dust had settled, the Turkish controlled Armenian city states also rebelled and united with the Mesopotamian city states in order to form a Middle Eastern alliance, which named after the ancient civilization of Babylonia. All this brought Turkey on the brink of collapsion, which suited Catherine and Russia extremely well as Turkey couldn't anymore militaristicly threaten Russia.
Nontheless, the Ottoman Emperor sent a small army through the Caucasus Mountains in order to surprise the Russians. This proved to be a mistake as the Russian Cossacks encountered and quickly annihilated the Ottoman Cavalry Platoons just north of the Mountains.
The war was at a standstill as neither side felt the need to attack eachother. The Turks were too weak and troubled by their internal disputes that a direct attack against Russia would surely collapse the deteriorating Ottoman rule. Catherine on the other had no real interest to conquer Turkish lands, at least not yet while the Ottomans were still standing and able to resist an invasion.
However, apparently the Nordic Viking Empire was not well informed about the situation of the Russo-Turkish War and in 1820 they declared on Russia as they probably thought that they could catch Russia off guard.
The Norrmen had the elements of surprise on their side, but in the end they failed to exploit it. When the Viking army crossed the border to Russia started to advance towards weakly defended Murmansk, Catherine ordered all her European Platoons to ride north and encourter this new threat. The Russian reinforcements would have not made in time unless the Viking General had not ordered the cannons to soften the way first. The Norrmen wasted precious time while bombarding the defences in the freezing cold of the Arctic. As a result the Russians had time to build up the defences and gather troops. In order to win time the Russian garrison orchestrated a succesful attack against the sieging army.
The Russian attack slowed the Viking assault even more and they were still doubtful about making the final push, when the Russian Imperial Cavalry Platoons rode straight into their right flank.
The Viking army was completely surprised and the Russian cavalry Platoons crushed the army without second thoughts. Murmansk was saved.