Complex sentence: Brandeis understood the support that Blackstone would raise for the "Memorial" would enable President Wilson to accept and endorse American Zionism and the later British Balfour Declaration of 1917, which set the course for the establishment of the State of Israel.
Split into simpler sentences: Brandeis understood the support that Blackstone would raise for the "Memorial" would enable President Wilson to accept and endorse American Zionism and the later British Balfour Declaration. The Balfour Declaration of 1917 set the course for the establishment of the State of Israel.