Let me explain what I'm talking about. Looking at WW1 and WW2, especially on the European fronts, we can see frontlines, which are completely secured on both sides so no army can walk through them without a fight, everything that's behind the frontlines is occupied and garrisoned and cut off from the rest of the enemy territory. Whoever runs out of territory to retreat to or resources to continue fighting loses the war.
As an example of what I'm talking about, I want to look at 1812 Napoleon invasion of Russia. He assembled 600k men, clearly not enough to create a proper frontline and occupation of modern days, yet he outnumbered the enemy. He assembled his army into one big blob and marched into Russia, only to be kited around, harassed, denied pillaging, he lost a lot of soldiers, then he caught up to the Russian army and won in Borodino, securing the battlefield and forcing enemy to retreat, he entered Moscow, only to get denied capitulation and retreat.
So here's what I'm asking. Most wars of that period never had army sizes of more than hundreds of thousands - not enough to form frontlines in the HRE, Sweden (as in Finland), Russia and Baltic states, Poland, Austria and France - major battlefields of the time. Armies of the time already had cannons, so cities were never walled, and needed large garrisons to protect them, reducing attacker's possible army size a lot. Also, population was decentralised, so you needed to hold onto more of territory to actually secure a win. As such, the "kiting and harassment" strategy could work for any defender and not only Russia. So the question is - what were the requirements of actually securing a military victory at the time if the enemy doesn't want to surrender? What was Napoleon's (or every other attacker's) plan to close out a war, considering that every battle possible goes their way?
I'll say upfront: this is a very complex and in-depth question, and I can only answer part of it. The time period you've identified stretches a good 300-350 years and warfare and military thinking underwent numerous massive changes in this period. I can't speak much to the conduct of warfare from the 16th to 17th centuries, but I can talk about the dominant methods of strategic thinking in Western Europe in the latter half of the 18th century and the changes the French Revolution and Napoleonic Wars wrought on it.
The general characterisation of warfare in the late 18th century that emerges from the historiography of the period is this: wars were frequent, and strictly limited. The process of the ‘stately quadrille’ – a constant diplomatic and military jockeying for territory between major powers such as Austria, France, Russia, and Prussia – required monarchs to maintain standing armies of professional soldiers, but the ‘crab bucket’ effect on diplomacy should any one power achieve absolute dominion and the unwillingness of what were for the most part absolute monarchies to risk internal instability on military gambles meant that wars were, for the most part, limited.
Armies were small, as the unpleasant nature and harsh discipline of military service meant recruitment was difficult, and were also the monarch’s chief tool of power-protection and the guarantor of their monopoly of force, which made them precious. Therefore, generals were not encouraged to pursue bold yet risky manoeuvres, and in particular tended to pay attention to their lines of supply, ensuring firstly that their soldiers remained loyal and capable of fighting, and secondly that the land they were fighting over was not overly devastated by extensive foraging.
This attention to supply made fortification particularly important. Moving an army is a major task, and keeping it supplied an even bigger one. Generally armies would not move by a single road, but major routes that were capable of supporting the movement of troops and guns were relatively few, which meant that strategically-place fortresses designed to resist artillery fire could effectively block the advance of an enemy army. The enemy couldn’t bypass these forts, since the garrison could wreak havoc on their supply, and armies did not usually have sufficient forces to screen a fortress for any significant length of time. A siege would therefore be necessary, with the besiegers digging siege-lines and emplacing cannon to batter breaches in the walls and either force a surrender or facilitate a storm.
When besieging a fortress, an army had to be stationary, making it possible for an enemy to outmanoeuvre them and threaten their lines of supply. In general, commanders would prefer to retreat to protect this vulnerability, and enemy commanders would prefer to let them, since offering battle would risk precious soldiers, and allowing a retreat achieved the desired goal anyway.
This isn’t a comprehensive picture, but the vision of late-18th-century European warfare as being principally concerned with manoeuvre and positioning in order to force a retreat is fairly well-supported by the available evidence.
All this changed with the advent of the French Revolutionary Wars. Where before, wars had been fought for limited goals – the capture of a specific section of territory, usually – the French Republic found itself fighting a war for survival. The Coalition would not rest until the Republic had been overthrown, and the Republic’s leaders had declared their intention to destroy the monarchies of Europe. Those monarchies feared revolution at home should they fail to crush the French.
Since the Revolution had largely accelerated the atrophy of the Royal Army, the Republic instituted several reforms – the introduction of new forms of staff-work, organisation by divisions, and, most importantly, the levée en masse. This was the first modern form of conscription, and it meant that instead of a small professional army French Generals - many of whom were new to the business of warfare and thus unfamiliar with the received wisdom of their opponents - were in command of a huge force of dubious quality. The Republic’s ability to supply its new armies was marred by the economic depression that France still suffered, mass corruption in the commissary, and the chaos that marked most aspects of the Republican state. Therefore, soldiers needed to live off the land, and French troops became adept at foraging for food on enemy – or their own – territory.
This change in how armies moved and fought prompted changes in strategic thinking. The Republic, suspicious of its new army and its generals (several prominent noble generals like Lafayette had attempted military coups), sent ‘representatives of the people’ to oversee the war effort – effectively political commissars. These men, who were universally not soldiers, generally demanded an aggressive stance from generals and had the power to execute those who did not cooperate with their demands. Thus French commanders began to focus on engaging and destroying the enemy, rather than manoeuvring him from a position.
What Napoleon (and several other French generals, but I’ll use Napoleon as an example since he perfected this style of warfare) did was to synthesise these two approaches; he had been trained in the old mentality of war at France’s military schools, and was a product of the constant struggle of the Revolutionary armies. The rational was this: the surest way to bring the enemy to negotiation was to destroy his ability to fight, and the best way to do that was to shatter his army.
Therefore, Napoleon took an approach of rapid manoeuvre to cut or threaten enemy supply lines, using the superior mobility of French troops and their heard-learned ability to live away from their own supply lines to force the enemy to move away from their positions. Then, rather than allow the enemy to withdraw, French armies would instead close in for the kill, using their superior staff organisation to coordinate the concentration of multiple divisions that had been moving separately to achieve a local numbers advantage. This process meant that the French could usually not choose their battlefield precisely, but it also denied the enemy that possibility.
Once battle had been joined, the French goal was to outmanoeuvre the enemy and cause a rout, followed by a vigorous pursuit that would prevent the remnants of the enemy army from reforming. If possible (it very often wasn’t), Napoleon sought to cut off enemy lines of retreat as well. This pursuit can be seen in its platonic form after Jena-Auerstadt, when the French Army pursued the defeated Prussians across almost the entirety of the country, ensuring that Prussia would not be able to put another army in the field against France for almost eight years.
Finding the enemy, outmanoeuvring him by threatening his supply lines or other positions important to him (such as his capital) via a serious of rapid marches, the coordination of disparate forces by means of superior staff organisation, and thence proceeding to defeat and pursue the enemy to destruction, can therefore be seen as what we might call Napoleon’s preferred ‘strategic method’. It didn’t always work, especially when facing an enemy that could afford to trade space for time and overstretch the Grande Armée’s supply lines, as happened in Russia and nearly happened prior to Austerlitz, but on the rich and infrastructure-dense areas of western and central Europe it was highly effective.
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