Potemkin could hardly fail to see an invitation in this language.

Could anyone explain if there's anything unusual in the language with which Catherine wrote to Potemkin? In my eye, it was normal, but why did the author say it was an invitation? Thanks!

When he returned to the army in the south, it was with Catherine’s permission to write to her privately. She was surprised that he was slow to use this privilege. On December 4, 1773, she prompted him:

Sir Lieutenant General and Chevalier: I suppose you have your eyes so thoroughly trained on Silestra [a Turkish fortress on the Danube under siege by the Russian army] that you haven’t time to read letters.… Nonetheless I am certain that everything you undertake can be ascribed to nothing but your ardent zeal toward me personally and toward the dear fatherland which you love to serve. But since I very much desire to preserve fervent, brave, clever, and skillful individuals, so I ask you not endanger yourself.… Upon reading this letter you may well ask: why was it written? To which I can offer the following reply: so that you had confirmation of my opinion of you, for I am always most benevolent toward you.Catherine.

Potemkin could hardly fail to see an invitation in this language.