ship of Cromwell and Louis XIV. He was, however, obliged to make
in 1655 a treaty with the Swedes, in consequence of which he joined in
the invasion of Poland, and greatly contributed to the victory at
Warsaw. Austria, Holland, and Poland vehemently protested against this
alliance with Sweden. Cromwell, however, who believed the Protestant
cause to be in danger from the King of Poland, sent William Jepson as
his ambassador to the elector, whom in letters he compliments in the
highest terms for his service to the Protestant religion. But Russia and
Austria declaring in favor of Poland, he, by the mediation of Austria,
concluded a convention with Poland at Wehlau, by one of the stipulations
of which he obtained the entire sovereignty of Prussia, and in 1678
completed the conquest of all Pomerania by the taking of Griefswald and
Stralsund. The death of Charles Gustavus freed him from an adversary who
would probably have endeavored to prevent the execution of this treaty,
which was confirmed by the treaty of Oliva. Frederick, now at peace with
his neighbors, directed all his attention to promote the welfare of his
subjects by favoring all internal improvements; the ruined towns and
villages were rebuilt, new roads made, waste lands cultivated, commerce
encouraged, and many useful establishments founded.

[Illustration: The Great Elector withdraws from the association of the
Dutch nobility.]

In 1672, however, Holland being threatened by Louis XIV., he concluded a
treaty with the republic, engaging to furnish 20,000 men for its
defence. He also contributed to induce the emperor: Denmark, Hesse
Cassel, and several German princes to join him against France. But
though his advance into Westphalia induced the French to quit Holland,
the campaign was rendered unsuccessful by the slowness of the Austrian
general, and he was forced to abandon Westphalia to the enemy. The
Austrians leaving him, and the Dutch neglecting to send him subsidies,
he was obliged to make a convention with France in 1673. The French were
to evacuate Westphalia and pay him 800,000 livres, he promising to
withdraw from his alliance with Holland, and not to support the enemies
of France; yet he reserved to himself the right of assisting the German
emperor in case of attack. This happened in 1674, when he invaded Alsace
with 16,000 men, and joined the Imperial army; but the Austrian general,
Bournonville, avoided a battle, contrary to the advice of Frederick, a