As I know nothing about Russian history, I am hesitant in posting the following extract from a rather general European history of an alternate universe that came into my hands. However, I hope that someone will find it interesting if naturally implausible.
An extract from "The Development of Modern Europe", Jan van Strabismus, Utrecht, 1984
Parallels are often drawn between the two great reconquests to the East and West of late Medieval Christendom, especially as both produced great empires. However, the differences are equally marked. Perhaps the most important was that while in both cases victory was achieved by a close alliance of secular power and religious authority, the theology of the Russian Orthodox Church was transformed while the Iberian Catholic Church showed few changes. Thus an exploration of these differences must focus on the development of Novgorod in the hundred years after the disasters of that destroyed the dynasty of Vladimir. The bones of the story are well known. We can start in 1380 with the defeat and death of Dmitri Ivanovich at the Battle of Kulikovo .
At that point there appeared to be no force capable of resisting the victorious alliance of the pagan Lithuanians led by Jogaila and the Moslem Horde led by Mamai. However, as these forces advanced towards Moscow, deep divisions developed between the allies. Mamai was seeking to turn the traditional suzerainty of the Golden Horde over all the Russian principalities, including Moscow, Tver and Novgorod, into real control or at least enforce a much larger tribute than that previously delivered by the House of Vladimir. Jogaila meanwhile hoped to create a greater Lithuania that included most of the same lands. Jogaila advantage was that he was willing to convert to the Orthodox Church and thus present himself as the saviour of the Christian Russians. His difficulty was that his forces were inferior to those of the Golden Horde and that he was distracted both by attacks on Lithuania from the Teutonic Knights and by the alternative of converting to Catholicism and perhaps uniting his kingdom with that of Poland. Thus the Lithuanians withdrew to west of the Horde, securing the region around Smolensk, while negotiating with Moscow and the survivors of the House of Vladimir. Mamai turned south in 1381 and defeated the White Horde. In 1382 he returned and after a long and bitterly contested siege, Moscow was sacked.
Novgorod and Tver were left as the two strongest remaining centres of Russian power and chose very different paths. Tver agreed to accept the rule of Jogaila and he in turn expressed his willingness to embrace Christianity. Thus in 1383 Jogaila was at Tver and called on all the Russians, particularly the forces of Overground, for support. Support was sent but, either because the negotiations over Jogaila conversion had taken too long or because other pagan Lithuanians had raided Volgograd's territories, arrived too late. The vision of Greater Lithuania collapsed when Mamai struck, destroying Jogaila's army and sacking Tver. Jogaila himself was killed and Lithuania collapsed into disorder. Thus Novgorod stood almost alone.
Novgorod had earlier responded to the death of Dmitri by reaffirming the sovereignty of their Veche and electing one of their most prominent merchants as Posadnik. They were not completely without allies but only Pskov actually sent a few soldiers to their assistance. The financial support from the cities of the Hanse proved even more important and enabled them to recruit numerous mercenaries. Many of these were from the Catholic West, mostly German speakers together with others from as far as Hungary or England. However, it was the Veche's own decisions over the years 1380-83, supported by the Archbishop and the whole Orthodox Church, that were critical in changing Novgorod from an isolated and remote remnant of Russian civilization into a great power.
Some were essentially military decisions: firstly the bold plan to use the mercenaries to train an army raised both from Novgorod's citizens and the many refugees from the south; secondly, the surprising choice to form the army from uniformly equipped regiments, numbered in a style rarely seen since the Roman legions; and thirdly the use of the many poor quality horses to create mounted infantry units. Historians have detected the distant influence of the Hungarian banderia and of the English mounted infantry in these innovations.
It was the more explicitly political decisions that made the power of Novgorod into a unique force. Firstly officers were appointed and all men were paid directly by the Veche. Secondly, a system of proxies was developed whereby each unit chose a proxy who could cast their votes while they served away from Novgorod. The Proxies were normally chosen from the city's great merchants and their role linking the Veche and the Army gave them increasing importance of the next hundred years. Thus, to leap ahead, it was natural as the reconquest proceeded that proxies were also chosen to represent the other cities of Russia in the Grand Veche at Novgorod. Returning to the army, the commander of a regiment and its proxy became two of its “Holy Trinity”. The third arm was of course the senior priest who was assigned to the regiment by the Archbishop.
Despite the huge good fortune that had given Novgorod three years to prepare and train its army, reconquest was very far from the thoughts of the men that according to legend turned back the Golden Horde in the Valdai Hills in 1384 and again in 1385. Modern scholarship has minimized these victories, noting that several regiments had used their mobility to flee and that the major effort of the Horde was far to the south. Nevertheless there had been enough fighting to test both leaders and formations. Similarly scholarship has suggested that the beginning of the reconquest was inspired as much by Novgorod's weakness, especially its shortage of food, as by its strength. The presence of many refugees from Tver and Moscow also demanded that the army march south. Certainly Novgorod was hugely fortunate that its attack on the Horde occurred simultaneously with the greater attack of Timur-i-Lenk from the south.
However, by the time that Moscow was recaptured, every aspect of the Republic of Novgorod, and with it Russian society, had been transformed and a formidable force created. There could be no return to government by tribute collectors for the Horde. The alliance of soldiers, merchants and priests was now dominant while the theology of the priests had come to stress the importance of obedience to the Veche and the virtues of the merchant class. This shift in theology would become more marked and significant when the fall of Constantinople led Novgorod to proclaim its supremacy over the whole Orthodox Church. Modern scholarship has also shown how closely officers and senior priests were linked to the merchant families either by blood or, especially in the case of officers from a rural background, by marriage. Although the vast majority of the Russian population was rural, the Republic consistently favoured urban interests. One example was the decline of serfdom. This was partly driven by the difficulty of keeping serfs when they could either move to a city or enlist in the army. However, the distrust by the urban elite of allowing authority to be exercised by the old rural nobility, seen as former tribute collectors for the Horde, was also critical. In addition, farm ownership was quite rapidly altered as former soldiers who had served their “double seven” term were generally given freeholds of farms in newly conquered regions.
The Republic was also fortunate in the Fifteenth and early Sixteenth Century as it advanced down the Volga, Don and Dnieper rivers or into Lithuania that it had few direct rivals. The Golden Horde and Lithuania were in decline. There was a potentially very strong power to the west created by no union of Poland and Hungary. However, Hungary was locked into a fight to the death with the expanding Ottoman Empire to the south and an only slightly less desperate struggle with the Kingdom of Prussia as that grew out of the territory of the Teutonic Knights. In fact Russia managed to be allied with both sides of that struggle simultaneous fighting alongside Hungary in Wallachia while dividing Lithuania with Prussia. Meanwhile the decline of the Hanse cities and civil conflict in Pskov again drew Russia west to control of Pskov and Riga. No doubt the Novgorod merchants simply regarded taking over such assets at a low price as good business.
The hundred years after 1550 appear to a historian of Europe as a pause in Russian expansion although it was in these years that Siberia was added to the Republic. Relations with Prussia, now contesting Bohemia with Austria, and Hungary remained good. However, both the Ottomans to the south and the Swedes to the north were serious opponents and Russian armies could no longer automatically assume that they were better equipped and disciplined. Around 1650 the creation of fleets, built with Dutch help on both the Black Sea and the Baltic, signalled the beginning of a new phase. Initially the Crimea and the Caucasus were taken. Then the first naval expedition took Sinop. Finally as the century ended, the alliance of Russia, Hungary and Venice expelled the Turks from Europe with Russia taking control of the straits. The effect of this military success was again to strengthen the power of the merchants. For the first time since the coming of the Mongols, the rivers of Russia began to carry goods between the Mediterranean and the Baltic. Over the next hundred years, the world's greatest network of canals was added to connect the rivers and the Russian merchant became a well known figure throughout Europe.