The Century of Redemption
Rav Yehuda taught from Kabbalah that 1840 began the Year of Redemption, which was not a single year but "a century, from this day until 1939," the days of Mashiach. If powerful practical steps were not taken, this opportunity would be lost, and the next long "year," beginning in 1940, would be one of great hardship, when Hashem would gather the scattered ones "with an outpouring of wrath." The outcome, the return to Eretz Yisroel, would be the same, but under far harsher circumstances.
Source: Rav Yehuda Alkalai, on the year of redemption