He decided on flight to England. It was a desperate measure, and was discovered and frustrated at the last moment. The King of Prussia laid the blame on English diplomats, though they had done nothing to help the Prince. There was talk of an Austro-English war at that time. "I shall not desert the Emperor even if everything goes to the dogs," wrote the irate father. "I will joyfully use my army, my country, my money and my blood for the downfall of England." He was so enraged by the attempted flight that he might have gone to the extreme of putting his son to death, but an old general, hearing of the probable fate of the Crown Prince, offered his own life for that of Frederick, and raised so vehement a protest that the runaway was merely put in prison.
His confinement was not as strict as it would have been, had the gaolers followed the King's orders. He had to wear prison dress and sit on a hard stool, but books and writing materials were brought to him, and he saw his friends occasionally. Lieutenant von Katte, who fled with him, was executed before the fortress, and the Prince was compelled to witness the punishment of the companion with whom he had practised music and other forbidden occupations.
By degrees, the animosity of Frederick William toward his eldest son softened. He was allowed to visit Berlin when his sister Wilhelmina was married to the Margrave of Baireuth, after four kings had applied for her hand, among them the elderly Augustus of Poland and Charles XII of Sweden. The Castle of Rheinsburg, near Neu-Ruppin, was given to the Prince for his residence. He spent happy hours there with famous men of letters in his circle, for he was actually free now to give time to literature and science. He corresponded frequently with Voltaire and became an atheist. He cared nothing for religion when he was king, and was remarkable for the religious toleration which he extended to his subjects. But the harsh treatment of youth had spoilt his pleasant nature, and his want of faith made him unscrupulous and hard-hearted. He grasped at all he could win, and had every intention of fulfilling the commands laid upon him by the Testament which his father wrote in 1722 when he believed himself to be dying;—"Never relinquish what is justly yours."
It was far from his intention to relinquish any part of his dominions, and, moreover, he set early about the business of conquering Silesia to add to his little kingdom. Saxony should fall to him if he could in any wise win it. There was hope in that fine stalwart body of men his father had so well disciplined. There was courage in his own heart, and he had been reared in too stern a school to fear hardships.
In 1740, Frederick received his dying father's blessing, and in the same year the Emperor, Charles VI, left his daughter, Maria Theresa, to struggle with an aggressive European neighbour. She was a splendid figure, this empress of twenty-three, beautiful and virtuous, with the spirit of a man, and an unconquerable determination to fight for what was justly hers. She held not Austria alone but many neighbouring kingdoms—Styria, Bohemia, the Tyrol, Hungary, and Carpathia.
Charles VI had endeavoured to secure his daughter's kingdom by means of a "Pragmatic Sanction," which declared the indivisibility of the Austrian dominions, and the right of Maria Theresa to inherit them in default of a male heir. This was signed by all the powers of Europe save Bavaria, but Frederick broke it ruthlessly as soon as the Emperor died.
In high spirits Frederick II entered on the bold enterprise of seizing from Maria Theresa some part of those possessions which her father had striven to secure to her.
Allies gathered round Prussia quickly, admiring the 80,000 men that the obscure sovereignty had raised from the subjects of a little kingdom. France, Spain, Poland, and Bavaria allied themselves with the spoiler against Maria Theresa, who sought the aid of England. She seemed in desperate straits, the victim of treachery, for Frederick had promised to support her. The Battle of Molwitz went against Austria, and the Empress was fain to offer three duchies of Silesia, but the King refused them scornfully, saying, "Before the war, they might have contented me. Now I want more. What do I care about peace? Let those who want it give me what I want; if not, let them fight me and be beaten again."
The Elector of Bavaria was within three days' march of Vienna, proclaiming himself Archduke of Austria. Maria Theresa had neither men nor money. Quite suddenly she took a resolution and convoked the Hungarian magnates at Pressburg, where she had fled from her capital. She stood before them, most beautiful and patriotic in her youth and helplessness. Raising her baby in her arms, she appealed to the whole assembly. She had put on the crown of St Stephen and held his sword at her side. The appeal was quickly answered. Swords leapt from their scabbards; there came the roar of many voices, "Moriamur pro rege nostro, Maria Theresa!" ("Let us die for our King, Maria Theresa.")
But Friedrich defeated the Austrians again and again in battle. No armies could resist those wonderful compact regiments, perfectly drilled and disciplined, afraid of nothing save of losing credit. Maria had to submit to the humiliation of giving up part of Silesia to her enemy, while the Elector had himself crowned as Emperor Charles VII at Frankfort. The English King, George II, fought for her against the French at Dettingen and won a victory. She entered her capital in triumph, apparently confirmed in her possessions. But Frederick was active in military operations and attempted to detach the English from her. He invaded Bohemia and defeated the imperial generals. He received the much-disputed territory of Silesia in 1745 by the Treaty of Dresden, which concluded the second war.