In June, Frederick the Great used the trench warfare method suggested by Wilhelm to shine in Saxony, inflicting a heavy defeat on the Austrian army led by Field Marshal Lassy.
After this battle, Marshal Lassi had to lead the remnants of the Austrian army back to Vienna, and Joseph II broke the teacup when he received the news, and then became angry and wanted to execute Marshal Lassy, but his mother, Queen Maria Theresa, made a message to the emperor to save Marshal Lassy Frederick, after his great victory, felt that his opportunity had come, and he felt that he should not go to Bohemia again, but should lead his army to Vienna.
On the same day he wrote to his younger brother, Prince Henry, ordering him to hold back the enemy in Bohemia, and that he would march his victorious army to Vienna.
When Prince Henry received Frederick's letter, he was taken aback by Frederick's idea, and immediately replied to Frederick: "My dear brother, it is not the best strategy to attack Vienna at this time, and our army should meet in Bohemia according to the original plan, so as to seize Bohemia.
If the target is changed to Vienna, even if it wins, our army will pay an extremely heavy price.
Austria and we will no longer have room for manoeuvre, and the European countries will certainly not sit idly by and watch us break through Vienna, and they will certainly intervene.
Prussia has not yet recovered from the wounds of the last war, my brother, I pray that you will preserve the future for Prussia.
But when Frederick received Henry's letter, he was furious, he never felt that he was so close to Vienna, and the thought of the shame of the Seven Years' War was like a dream, and every night Frederick had to grit his teeth and recite the name of Vienna and the woman to sleep.
Frederick was not willing to give up his thoughts on Vienna in this way, and he again wrote to Prince Henry: My brother, thank God, I never felt so close to Vienna, it was like a nightmare that entered my dreams every night, and I had to conquer this city and make all the people of this city kneel at my feet.
My brother, for the sake of the rise of Prussia, we must sweep Austria.
Now that Lassi has been defeated by me, and he has returned to Vienna with only 20,000 men, I must cherish the opportunity God has given me.
My brother, you must obey my orders, you must hold back the enemy in Bohemia, and I will join you as soon as I take Vienna, for the sake of Prussia.
Prince Henry had to take Frederick's orders to move forward step by step and instead attack the enemy in Bohemia.
In July, when the Prussian army was only about 200 kilometers from Vienna, Joseph II had to order the Bavarian Front to return to Vienna and at the same time recruit the defenders from all over the country to form the Vienna Garrison Corps.
Joseph II appealed to the nobles of the Holy Roman Empire, but few responded, all of whom were watching the war between Prussia and Austria.
Before the Prussians arrived in the city, the Vienna garrison corps ordered by Joseph II was established, which was still under the command of Field Marshal Lassy, and although Joseph II was angry at Lassy's defeat, he had to admit that only Lassi was the most likely person in Austria to resist Frederick.
At the same time, the Bavarian Front led by Leopold II had to give up their previous advantage in Bavaria to return to Vienna after receiving orders from Joseph II.
However, the process of reinforcement was not calm, and the Prussian cavalry led by Prince Ferdinand of Prussia stuck behind him like kraft candy, always surprising the Austrians by surprise, greatly delaying the speed of the Bavarian Front's reinforcements.
In August, the Prussian army, led by Frederick, arrived outside Vienna.
Frederick led his generals to a hill outside Vienna, pointed his whip at Vienna and said: "My generals, Vienna is before our eyes, the dream of a hundred years of Prussia is about to be realized in our hands, and I ask every soldier to devote himself to this battle with a sacrifice of his own life, and on the day of our victory, I will give every soldier who has participated in this war the wealth accumulated by Vienna over the centuries.
And you, you will be admired by all the Prussian people.
When you are old, you can hold your grandson and proudly tell him that your grandfather followed Frederick in the storming of Vienna and defeating the Habsburg dynasty that had been shining on Europe for hundreds of years, laying a solid foundation for the future of Prussia."
Just as the Prussian army appeared outside Vienna, Field Marshal Lassi was vigorously reorganizing his army.
The 20,000 men who returned to Vienna from the last defeat, the 30,000 men from Joseph II who had drawn the garrison from all over the place, and the 30,000 militia in the city, made a total of 80,000 men.
They had just over 200 guns, but thanks to the savings of the Habsburgs, the equipment of this army was of the best in Europe, and a large number of military horses were transferred into the army, including the royal horses in the royal horse farm of Joseph II.
Although the Austrians had much less artillery, they armed 30,000 cavalry, of which 20,000 were cuirassiers, which gave the Austrians confidence in holding Vienna.
After the arrival of the Prussians in Vienna, Frederick ordered the siege of the city, and he ordered all his soldiers to dig trenches outside the city to block possible reinforcements from the Austrians, and at the same time the more than 20,000 men he had urgently called up to the country after the last war were coming, and by that time a total of 100,000 Prussian troops would be gathered under the city of Vienna.
Frederick ordered his soldiers to dig trenches and his artillery to pour shells into Vienna, and the Austrian artillery and shells captured in the last battle were enough to last the Prussian army for half a month.
There were three trenches in front of his artillery position, in order to prevent the Austrians from raiding.
Joseph II urgently summoned Marshal Lassi and said: "My marshal, I can forgive you for the defeat in the last battle, but I will not allow you to lose this battle, which is where Vienna and my Habsburg dynasty have been built for hundreds of years.
My marshal, the fortunes of Austria for a hundred years have been entrusted to you".
And Lassi said to Joseph II: "Your Majesty, rest assured, I will defend Vienna with my life, but I have only one plea, if you are not evacuated from Vienna with Her Majesty the Queen."
Queen Maria Theresa, who was on the side, spoke: "Field Marshal Lassi, my son and I are not going anywhere, Vienna is our home, the place where the souls of our Habsburg ancestors return.
There are only two paths before us, Either the Prussians are defeated by us, and Frederick, who deserves to go to hell, kneels before us.
Either His Majesty the Emperor and I were captured by the Prussians, and the thousand-year-old glory of the Habsburgs was trampled on.
Field Marshal Lassi, Your Majesty and I have not only put the national fortunes of Austria in your hands, but also ours to you, and you must not fail to live up to the expectations that My Majesty and that of the Emperor have of you."