regno. But it was never forgotten by Honorius and the
papal curia. The pope even helped to arrange Frederick’s
marriage in 1225 to the heiress of the kingdom of Jeru-
salem, Isabella Yolande of Brienne. Frederick reiterated
his crusade obligations: under pain of excommunication
he would depart for the East before August 1227. In a
related matter, Frederick promulgated, in 1226, for the
Teutonic Knights the Golden Bull of Rimini, establish-
ing the foundations of their autonomous state in Prus-
sia. That same year the emperor attempted to convoke
a diet to restore imperial rights in northern Italy, but
his intentions were thwarted by the resistance of the
reconstituted Lombard League under the leadership of
Milan. The death of Honorius III in 1227 led to the elec-
tion of Gregory IX, who as cardinal had been friendly
to the emperor. But when plague struck the gathering
crusaders in Brindisi during late summer 1227, the
embarkation became a debacle; the emperor himself
sailed but immediately became ill, returning three days
later and postponing further departure to spring 1228.
Yet Gregory, long impatient with the emperor’s past
excuses, held him strictly to the terms of his promises
and excommunicated the emperor despite the latters
protestations.
Frederick nonetheless continued preparations for
the voyage east despite the spiritual ban and Empress
Yolande’s death shortly after giving birth to Conrad (IV).
In June 1228 the emperor reembarked with a small army
and arrived in Acre, where he found little support from
the local Syrian-Frankish baronage, the ecclesiastical
hierarchy, or the military orders. Despite such handicaps,
Frederick drew on his knowledge of Arabic and Muslim
culture to negotiate a favorable treaty with the Egyptian
sultan al-Kamil. The emperor next entered the Holy City
and crowned himself king of Jerusalem, basing his title
on his deceased wife’s claim and on their son Conrad’s
minor status.
The pope’s enmity did not slacken, however. War had
already broken out in Italy. Since any further actions in
Outremer were doomed to failure, the emperor set sail
and returned to Brindisi. Frederick quickly assembled
troops and swept the papal invaders back northward,
taking care to halt his victorious advance at the border.
Negotiations during the next year, 1230, culminated
in the treaties of San Germano and Ceprano. Gregory
absolved Frederick from excommunication, the territo-
rial status quo was restored, and the emperor promised
the Sicilian church freedom of prelatial elections and
other privileges. But otherwise nothing was decided
regarding the threatened encirclement of papal territory,
papal doubts regarding the emperor’s stance toward
ecclesiastical liberty, and the Lombard’s autonomy.
A fragile peace now restored, Frederick embarked on
his most memorable legal project—the codifi cation of
royal laws for the regno in Liber Augustalis, or Constitu-
tions of Melfi (1231). This work of synthesis organized
royal enactments with a view to centralize authority,
bureaucratize royal government, and weaken all other
non-royal intermediate jurisdictions.
But trouble now loomed in Germany, where young
King Henry’s weakly executed and unsteady policy of
alliance with imperial ministerials, towns, and lesser
aristocrats provoked opposition and demands from the
greater princes. Henry was compelled to issue Statutum
in favorem principum (1231), and his father had no
choice but to confi rm the same document a year later.
In constitutional terms the autonomy of the princes
was thereby somewhat strengthened, while restric-
tions on imperial cities were somewhat tightened. In
1232, Frederick imposed on his son an oath not to
pursue in the future his former policies, but Henry
nonetheless rebelled in 1234, and even allied himself
with the Lombard League. When Frederick himself
journeyed north in 1235, however, all resistance col-
lapsed. Henry submitted unconditionally to his father,
was stripped of his title and crown, and imprisoned for
the rest of his life in various castles. He died by suicide
in 1242.
Frederick now married again, this time to Isabella
Plantagenet, sister of Henry III of England. The emperor
proceeded to celebrate his triumphs at an imperial diet
in Mainz, where he promulgated a peace edict that cre-
ated the post of high court judge and proclaimed that
all rights of governance originated in the monarchy.
Frederick also staged a reconciliation with the Welfs by
creating the feudal principality of Brunswick-Lüneburg
for Otto, nephew of Otto IV.
Frederick returned to Italy, where he waged a military
campaign during 1236 against the Lombards. Winter
brought the emperor north again, this time to depose the
outlawed rebel Frederick II of Austria and Styria. The
emperor also arranged that his son Conrad was elected
king of the Romans in Vienna (1237). He journeyed
back to Italy, where his political fortunes now reached
their zenith; Frederick led his army to victory over the
League of Cortenuova, an alliance between Maitland
and Lombard. The vanquished Lombards became eager
to negotiate peace, but the emperor’s intransigence en-
couraged instead a spirit of desperate resistance among
a hard core of league members. Six cities chose to fi ght
on. His relations with Pope Gregory also worsened.
Frederick’s illegitimate son Enzio married at his father’s
urging the heiress to a large portion of Sardinia and, in
a calculated affront, immediately styled himself king of
that island, thereby ignoring papal claims to overlord-
ship. In 1239, the pope excommunicated Frederick a
second time, charging that the emperor had oppressed
the Sicilian church, impeded crusades, and assisted re-
bellious Romans. The real reasons for confl ict, namely,
the emperor’s ongoing struggle with the Lombards andFREDERICK II