With this object, during Charles XII.'s stay at Altranstadt (1706-1707), he tried to divert the king's attention to the Holstein question, and six years later, when the Swedish commander, Magnus Stenbock, crossed the Elbe, Gertz rendered him as much assistance as was compatible with not openly breaking with Denmark, even going so far as to surrender the fortress of Tenning to the Swedes.
Gertz next attempted to undermine the grand alliance against Sweden by negotiating with Russia, Prussia and Saxony for the purpose of isolating Denmark, or even of turning the arms of the allies against her, a task by no means impossible in view of the strained relations between Denmark and the tsar.
Gertz first suggested the marriage between the duke of Holstein and the tsarevna Anne of Russia, and negotiations were begun in St Petersburg with that object.
From Turkey at Stralsund, Gertz was the first to visit him, and emerged from his presence chief minister or "grand-vizier" as the Swedes preferred to call the bold and crafty satrap, whose absolute devotion to the Swedish king took no account of the intense wretchedness of the Swedish nation.
Gertz, himself a man of uncommon audacity, seems to have been fascinated by the heroic element in Charles's nature and was determined, if possible, to save him from his difficulties.
His chief financial expedient was to debase, or rather ruin, the currency by issuing copper tokens redeemable in better times; but it was no fault of his that Charles XII., during his absence, flung upon the market too enormous an amount of this copper money for Gertz to deal with.
Gertz hoped, however, to conclude peace with at least some of Sweden's numerous enemies before the crash came and then, by means of fresh combinations, to restore Sweden to her rank as a great power.
It must be admitted that, in pursuance of his "system," Gertz displayed a genius for diplomacy which would have done honour to a Metternich or a Talleyrand.
Simultaneously, Gertz was negotiating with Cardinal Alberoni and with the whigs in England; but all his ingenious combinations collapsed like a house of cards on the sudden death of Charles XII.
Perhaps Gertz deserved his fate for "unnecessarily making himself the tool of an unheard-of despotism," but his death was certainly a judicial murder, and some historians even regard him as a political martyr.
Von Beskow, Freherre Georg Heinrich von Gertz (Stockholm, 1868).