War of the Fourth [actually Fifth o.t.l.] Coalition
Having defeated Prussia, Austria and [albeit barely] Russia with minor [although critical casualties], Napoleon's attention turned to Spain to exploit its chaos following the invasion of Portugal. Also, Napoleon faced several insurrections in his occupied territories. Despite this, Napoleon still wanted to intervene in Spain. But Portugal had to be subdued first.
Meanwhile, Russia had crushed the Ottomans in the Balkans and left the Ottoman Empire on the defensive without any Napoleonic War-era territorial gains still under Ottoman control in 1807, allowing the Russians to face Napoleon alone before being defeated in East Prussia as the Russian 'Romanian Principalities' were liberated and strong enough to deal with the Ottomans alone along with Bulgaria's first taste of 'independence'. After failed Ottoman offensives, the empire signed a peace treaty with the Romanian states and Russia [along with France for the latter].
[Peninsular War is mostly similar to reality, but with minor butterflies in favour of Britain due to the changes in warfare and Napoleonic garrisons. Note that there are fewer Ottoman, Russian, British and French ships in the Mediterranean as a result of the changes. The Scandinavian Wars would end in a stronger Russia as a result of more Russian soldiers and ships, with Sweden being weakened.]
In August 1809 [after some delays], the heavily weakened Austrian Empire finally declared war on France. There would be attempts to support the Austrians by opportunistic [later weakened] Hungarian nationalists, but the defeat of Austria in December 1809 and the threat of Russian and Serbian intervention prevented actual Hungarian assistance. In any event, the Hungarian Government was in chaos as a result and had to clamp down on the rebels, like the situation in Napoleon's Rhine Confederation. An Austrian Empire with more discontent yet further reduced in size to its German core was the result after a peace treaty was signed in February 1810, but only some hinterlands were lost. It was still for nothing, though.
War of the Fifth Coalition
https://en.wikipedia.org/wiki/War_of_the_Fifth_Coalition
After the Austrian Empire declared war on 9 August with a secret offensive against Napoleonic Bavaria and Hungary, Napoleon mobilised his armies just as Spain was about to be defeated. In fact, Spanish and British ships attempted a failed landing on the French coast at Walcheren, and the losses compensated those of 1807 without captures. However, the defeat of his armies by Austria and German nationalists resulted in Napoleon going on a maximum effort to defeat the enemy with an offensive. The Dalmatian, Italian and Grand Armies were called to defeat Austria after the near loss of a Bavarian corps and Davout to an encirclement by Austrians and Bavarian rebels. After the Austrian retreat from Landshut on 21 August, the Serbian Army attempted to intervene, but the Hungarian puppet regime of Napoleon prevented Serbian advances into Central Europe. In fact, quarrelling within the Serbian government stopped the troops from helping Napoleon. But Serbia and Russia kept Hungary and Romania from intervening initially.
Source:
https://en.wikipedia.org/wiki/Battle_of_Teugen-Hausen
During the campaign, it was noted that the Austrians decisively defeated Davout, Lefebvre and the French-Bavarian troops in the province of Bavaria. The Austrian troops pursued aggressively compared to reality and the troops were encircled, which resulted in Napoleon speeding up his attack orders. In support, the encircled troops broke out and left for Teugen-Hausen to join Napoleon. The Isar River was crossed and Ingolstadt fell, along with Regensburg. It was believed that support from other troops would encircle the Bavarians when Haugen and Sol An Der Danau were captured. However, at Dünzling and Schneidert, Rosenberg encountered and was fought by Montbrun's cavalry and a division. With less than 14,000 troops, Montbrun scored a victory against the IV Armeekorps throughout the day, using the wooded terrain to good advantage and sending a cavalry charge that defeated the attackers. Meanwhile, Regensburg was captured with heavy losses to both sides for their era's formations. Teugen-Hausen was assaulted by Austria and the Austrians were defeated with heavy losses for the French-Bavarian remnants nevertheless. By the end of the day, the Austrians had inflicted a corps' worth of casualties with moderate losses, but the defeat of Archduke Charles would spell Austria's doom.
Source:
https://en.wikipedia.org/wiki/Battle_of_Abensberg
At Abensberg, orders to withdraw were received with delay that V Corps was endangered with encirclement. Bachl was found with French cavalry marching into the village. Having become isolated from his supporting dragoons, Austrian General Thierry and his men were chased into the woods by Jacquinot's horsemen until they were encircled. By the afternoon, the troops were lost to the Austrian cause. The arrival of Jaquinot's cavalry surprised Schustekh and the Austrians were routed decisively, with heavy losses for the cavalry and IV Corps, which had lost troops as reinforcements following the previous day's Bavarian defeat to the III Corps. General Vandamme assaulted the crossing at Siegenburg, but it was useless under heavy resistance, so he decided to attack northwards, crossing the Danube at Abensberg and advanced to Kirchdorf from the south. Here the Bavarians and Württembergers located Bianchi with his reinforced brigade and a cavalry squadron. Pfeffenhausen was captured and an aggressive pursuit by the French-Bavarian II Corps [formed from the remains of the Bavarian Army] brought the Austrian IV Corps to a defeat with 5,000 casualties on the day of battle.
In the south, the Austrian Army and Tyrolean rebels were defeating Italian troops until news of a Russian offensive into Romania and [what would be ceded to] Hungary and the Hungarian declaration of war on Austria diverted Austrian troops from the Italian front to the Danube. Archduke John left a large vacuum that was exploited by the Italian Army, which pursued the remnants of his army to the Danube and joined Napoleon. Russia was prepared to attack Austria as it advanced to reclaim its Polish and Hungarian territories and the threat further diverted resources that Archduke Charles' Army was defeated at Vienna. On 24 August, Regensburg was evacuated despite its earlier capture and the Austrian Army retreated in good order to Vienna, but not before a chaotic retreat from the fortress with 12,000 casualties. The subsequent encirclement took Charles and his II corps' remnants from the Austrian order of battle and Hungary prepared to intervene, leading to Austria's Danubian defeat.
Landshut was taken and with 5,000 French casualties, the Austrian Army under Von Hiller was encircled. Defeat at the city resulted in plenty of supplies being captured and the Austrians lost a corps left behind when the city was taken on 21 August. The next day, the Austrian IV Corps was enveloped and an attempt to destroy Davout's Corps for the last time was lost after the defeat. At Eckmühl, soldiers stormed the bridge and captured the town while Rosenberg's former corps lost even more troops that his forces [and himself] were no longer a threat to France. Austrian cavalry troops were defeated with heavy losses and Regensburg was captured easily after one day [23-24 August] of battle. Over the battle, the French were nearly repulsed before charging by Davout led the French into the city and Archduke Charles was injured and captured, causing a chaotic retreat that led to shelling and even several drowning casualties that were saved by surrender. Although Hiller won the battle of Neumarkt decisively by encircling French forces, he had to retreat when the French crossed the Danube and approached.
At Ebelsberg, Hiller was nearly enveloped by heavy losses and couldn't fight anymore, so he retreated after heavy shelling covered his escape. This was on 5 September and Vienna was about to be occupied in a week. Demoralised, Hiller retreated to Vienna and the Danube as fast as possible. The II French Corps' arrival contributed to his decision despite an actually fierce fought battle from strong defences. In Czechoslovakia, an attack by demoralised troops was repulsed with heavy losses and this contributed to the corps' destruction on 20 September, leading to the siege of Vienna and defeat of Ferdinand.
By 13 September, Vienna was threatened when shells fell into the city while the defeat of Archduke Ferdinand's Army in the Polish plains prevented the troops from reinforcing Marshal Johann Hiller and the demoralised troops. After an offensive against the Danube succeeded on 23 September following an initial defeat at Aspern-Essling with significant casualties, Hungary proceeded to declare war on Austria and Vienna was besieged. The Austrian capital was relieved by a last ditch offensive on 5 November, but the subsequent advance into Austria cut the Austrian army across the Danube into two and the isolated portion surrendered on 20 November. The remnants were defeated in detail that on 2 December, an armistice was signed with peace to be in effect from February 1810.
Sieges [of the previous coalition]
Siege of Kolberg [Source of the actual facts [similar to reality]:
https://en.wikipedia.org/wiki/Siege_of_Kolberg_(1807)]
With the defeat of Prussia, it was up to Sweden to transfer troops to Pomerania to reinforce Prussian garrisons and occupy them should they attempt to surrender. The presence of the Swedish Army strengthened the resolve of the Prussians to fight Napoleon and Kolberg was soon besieged, although heavily defended by Swedes along with Straslund. There was heavy enthusiasm among the Poles and Germans wanting to claim the city for their respective newly-formed 'national' puppet states, but heavy combat and an offensive kept the city besieged until 11 July, when supply starvation and the Russian defeat at Friedland contributed to the fortress's surrender.
https://en.wikipedia.org/wiki/Siege_of_Stralsund_(1807)
In this scenario, the Swedes drove the French out of Pomerania and German troops were used in the siege instead, resulting in the continued siege being prolonged. The end details are similar to reality, but one month later. However, the Swedish losses would result in Russia winning the Finnish War of 1808 decisively.
Source:
https://en.wikipedia.org/wiki/Siege_of_Danzig_(1807)
Like the Pomeranian fortresses, the city was another important strategic location, more so because of the resources present in it and the potential of defeating Napoleon's advance with natural boundaries and fortifications. The city could only be invested from the west and the anti-Napoleonic Coalition navies were still supreme over the French Navy, while the Vistula blocked further chances of encirclement. As a result, Danzig was a direct threat to the French left and threatened Napoleon as troops could be landed from the Baltic and encircle Napoleon's rear, leading to his defeat. In fact, Italian troops and ships planning for a 'Mediterranean Campaign' had to replace French resources shifted to Spain and the Atlantic with the intention of supporting Napoleon's Army by operating against Britain only for one of the fleets to be decisively defeated and the other to be scattered in Spain despite actually minimal losses.
Marshal Lefebvre and his 10th corps besieged the city until defeat by a failed counterattack. After the weather improved with clear roads and the fall of another fortress, the Swedes, Prussians and Russians were decisively defeated and Danzig was besieged again, but with gaps in the centre. Luckily, Swedish Naval operations assisted the fortress until the end on 10 June, when the loss of several salvaged ships to grounding deprived the Coalition of supplies to Napoleon, who used them to penetrate the fortresses' defences and stormed them, until the city surrendered early on 14 June along with surrounding Pomeranian Baltic towns.
Danzig finally surrendered on 14 June 1807, after the fall of several fortresses ordered to support the defenders such as the Weichselmünde fort, but Russian General Kamensky had fled with his troops earlier, and the remaining garrison surrendered shortly afterwards on the same day. The defenders had lost around 15,000 men during the siege, compared to the French losses of roughly 1,400 men. In response to Lefebvre's assistance, he was elevated in rank. Swedish losses hampered operations to the extent that the breakout attempts failed.
Siege of Graudenz: On 21 February, an advance into Graudenz besieged the fortress from 28th February although it was lifted by advancing Russian stragglers and the withdrawal of the besiegers until the Russian offensive failed by 15 March, but the 10 days of relief [from 5 to 15 March] allowed food to be supplied and the fortress resisted until 14 July 1807.