The authors contend that Husseini was himself partly responsible for the Holocaust. It was almost immediately after his meeting with Hitler on November 28, 1941, at which time the Palestinian leader demanded and received the cessation of all Jewish emigration to Palestine in exchange for Muslim support for the Axis, that Hitler convoked the Wannsee Conference. Having closed the door on the last possible escape route for the Jews, genocide became the "final solution."

It was Kaiser Wilhelm II who first set the template in his cynical World War I strategy of fomenting jihad among Muslim subjects in British, French, and Russian territories in the Near East and North Africa. One side-effect of this strategy was German complicity in the Armenian massacres, which could well have served as a model for Hitler's treatment of the Jews.

The Nazis were eager for this partnership. They established special
relationships with the Muslim Brotherhood, the Ba’th Party, the Young
Egypt movement, and radical factions in Syria, Iraq, and Palestine. Berlin
also hoped to build links with the kings of Egypt and Saudi Arabia.
In 1939, for example, Hitler met Saudi King Abd al-Aziz Ibn Saud’s
envoy, Khalid al-Qarqani, telling him: “We view the Arabs with the
warmest sympathy for three reasons. First, we do not pursue any territorial
aspirations in Arab lands. Second, we have the same enemies.
And third, we both fight against the Jews. I will not rest until the very
last of them has left Germany.”
Al-Qarqani agreed, saying that the prophet Muhammad had acted
similarly in driving all the Jews out of Arabia. A Muslim could make
no more flattering comparison. Hitler asked al-Qarqani to tell his king
that Germany wanted an alliance and would arm both Saudi Arabia
and al-Husaini’s men.14
But first, Hitler had to decide precisely how “the very last” of the
Jews were to leave Germany. As late as 1941, Hitler thought this could
happen, in the words of Hermann Goring in July, by “emigration or
evacuation.”15 Yet since other countries refused to take many or any
Jewish refugees, Palestine was the only possible refuge, as designated
by the League of Nations in 1922. If that last safe haven was closed,
mass murder would be Hitler’s only alternative.
The importance of the Arab-Muslim alliance for Berlin, along with
the grand mufti’s urging, ensured that outcome. And al-Husaini would
be present at the critical moment Hitler chose it.
…
But Hitler had a higher opinion of the grand mufti’s value. All his
other Arab or Muslim partners had followers in just one country; al-
Husaini had transnational influence. The grand mufti sought to prove
himself worthy of these high expectations. At the Bellevue, he met not
only Arab politicians but also exiled Muslim leaders from the USSR,
India, Afghanistan, and the Balkans.
Foreign Minister Joachim von Ribbentrop was impressed, telling al-
Husaini, “We have watched your fight for a long time. We have always
admired you, fascinated by your dangerous adventures. . . .” Von
Ribbentrop assured al-Husaini of the Reich’s support.20 The Germans
accepted al-Husaini’s claim that the Arab masses would rally to their
side if Berlin guaranteed independence from British and French rule as
well as stopping all Jewish immigration into Palestine. In March 1941,
Berlin secretly promised to support Arab independence.21 In October,
Berlin and Rome publicly announced that policy.22
Among themselves, German officials called al-Husaini the most important
Muslim cleric and leader of the Arabs in Lebanon, Syria, Palestine,
Transjordan (today Jordan), Iraq, and elsewhere.23 Hitler called
him the “principal actor of the Middle East, a realist, not a dreamer.”24
A contemporary U.S. intelligence assessment agreed, claiming al-Husaini
was seen throughout the Middle East as “the greatest leader of the
Arab peoples now alive.”25
In recognition of this estimate, Hitler gave al-Husaini a ninety-minute
meeting on November 28, 1941.
…
Hitler greeted him warmly, “I am most
familiar with your life.”
His Arab guest returned the compliments, pleased to find Hitler not
only a powerful speaker but also a patient listener. Al-Husaini thanked
the German dictator for long supporting the Palestinian Arab cause.
The Arabs, he asserted, were Germany’s natural friends, believed it
would win the war, and were ready to help. Al-Husaini explained his
plan to Hitler. He would recruit an Arab Legion to fight for the Axis;
Arab fighters would sabotage Allied facilities while Arab and Muslim
leaders would foment revolts to tie up Allied troops and add territory
and resources for the Axis.

But there was another consequence of the al-Husaini–Hitler meeting
to cement their alliance. A few hours after seeing the grand mufti
Hitler ordered invitations sent for a conference to be held at a villa on
Lake Wannsee. The meeting’s purpose was to plan the comprehensive
extermination of all Europe’s Jews.
Considerations of Muslim and Arab alliances, of course, were by no
means the sole factor in a decision that grew from Hitler’s own anti-
Semitic obsession. But until that moment the German dictator had left
open the chance that expulsion might be an alternative to extermination.
When Hitler first told Heydrich to find a “final solution,” the dictator
had included expelling the Jews as an option. Already, the regime
estimated. it had let about 500,000 Jews leave Germany legally during
seven years of Nazi rule. Yet if the remaining Jews could only go to Palestine,
and since ending that immigration was al-Husaini’s top priority,
emigration or expulsion would sabotage the German-Arab alliance.31
Given the combination of the strategic situation and Hitler’s personal
views, choosing to kill the Jews and gain the Arab and Muslim assets
necessary for his war effort was an easy decision.32
Consequently, Hitler ordered the Wannsee Conference to devise a
detailed plan for genocide.33 Since this decision was linked to the alliance
with al-Husaini he would be the first non-German informed about
the plan, even before it was formally presented at the conference. Adolf
Eichmann himself was assigned to this task.
Eichmann briefed al-Husaini in the SS headquarters map room,
using the presentation prepared for the conference. The grand mufti,
Eichmann’s aide recalled, was very impressed, so taken with this blueprint
for genocide that al-Husaini asked Eichmann to send an expert—probably
Dieter Wisliceny—to Jerusalem to be his own personal adviser for
setting up death camps and gas chambers once Germany won
the war and he was in power.34

"The Mufti was one of the initiators of the systematic extermination of European Jewry and had been a collaborator and adviser of Eichmann and Himmler in the execution of this plan... He was one of Eichmann's best friends and had constantly incited him to accelerate the extermination measures. I heard him say, accompanied by Eichmann, he had visited incognito the gas chambers of Auschwitz."

"In September 1943, intense negotiations to rescue 500 Jewish children from the Arbe concentration camp collapsed due to the objection of al-Husseini who blocked the children's departure to Turkey because they would end up in Palestine.‏²⁰¹

We combatted this enterprise by writing to Ribbentrop, Himmler, and Hitler, and, thereafter, the governments of Italy, Hungary, Rumania, Bulgaria, Turkey, and other countries. We succeeded in foiling this initiative, a circumstance that led the Jews to make terrible accusations against me, in which they held me accountable for the liquidation of four hundred thousand Jews who were unable to emigrate to Palestine in this period. They added that I should be tried as a war criminal in Nurenberg.

The Fuhrer then made the following statement to the Mufti, enjoining him to lock it in the uttermost depths of his heart:

1. He (the Fuhrer) would carry on the battle to the total destruction of the Judeo-Communist empire in Europe.
2. At some moment which was impossible to set exactly today but which in any event was not distant, the German armies would in the course of this struggle reach the southern exit from Caucasia.
3. As soon as this had happened, the Fuhrer would on his own give the Arab world the assurance that its hour of liberation had arrived. Germany’s objective would then be solely the destruction of the Jewish element residing in the Arab sphere under the protection of British power. In that hour the Mufti would be the most authoritative spokesman for the Arab world. It would then be his task to set off the Arab operations, which he had secretly prepared. When that time had come, Germany could also be indifferent to French reaction to such a declaration.

On november 28, 1941, three weeks after his arrival in Berlin, the mufti was received by Hitler. As recorded in the minutes of the meeting, Hitler urged his guest to remain patient:

At some not yet precisely known, but in any case not very distant point in time, the German armies will reach the southern edge of the Caucasus. As soon as this is the case, the Führer will himself give the Arab world his assurance that the hour of liberation has arrived. At this point, the sole German aim will be the destruction of the Jews living in the Arab space under the protection of British power.