I write these words as I fast in observance of Shivah Asar b’Tammuz — the Fast of the Seventeenth of Tammuz. The fast commemorates the breeching of the walls of Jerusalem during the siege that culminated in the destruction of the Temple. In point of fact, I write these words on the eighteenth of Tammuz. The fast was delayed in deference to Shabbat, which fell on the seventeenth of Tammuz this year.

The continued relevance of this minor fast is understandably questioned by many. Repeatedly continuing to mourn the destruction of Jerusalem and the loss of Jewish national sovereignty when Jerusalem is a vibrant, modern Jewish city at the political and spiritual heart of a beautiful, living, sovereign, free and democratic Jewish state seems to some Jews to be spiritually obtuse, scandalously lacking in gratitude, and insensitive to the miraculous nature of the State of Israel.

I am not immune to such feelings of cognitive dissonance and spiritual inconsistency in maintaining this historic commemoration. After struggling with the contemporary tensions inherent in this fast day, however, I remain committed to its observance. In fact, I am convinced that this year’s Shivah Asar b’Tammuz offers a uniquely compelling message, especially to American Jews.

It was 240 years ago, on Shivah Asar b’Tammuz 5536 (that is, July 4, 1776) that the Declaration of Independence was signed in Philadelphia.   (This calendrical confluence recurs not infrequently.) It is tempting to see irony in the fact that Jews were mourning and fasting and looking back in time to the losses of antiquity just as the American founding fathers were attending the birth of a nation and inaugurating a future of unprecedented freedom and opportunity, full acceptance, and genuine enfranchisement for the Jewish people.

It is tempting to identify in the founding of the United States on Shivah Asar b’Tammuz fulfillment of biblical prophecy. Zechariah (8:19) foretold: “The fast of the fourth month (i.e., Tammuz)… shall become an occasion for joy and gladness, a happy festival for the House of Judah.” The events of 17 Tammuz 5536 (the “fast of the fourth month”) indeed are observed as “a happy festival” (though marked according to the Gregorian calendar!) — worthy of celebration, “joy and gladness” by the “House of Judah” in the twenty-first century. The historic alliance and friendship between the United States and the State of Israel accounts in no small part for the Jewish significance of this modern “festival.”

The modern history of Shivah Asar b’Tammuz is not all cheerful news for the House of Judah. This year’s fast represents a dark historic anniversary, far more recent and in many ways more compelling than the breeching of ancient Jerusalem’s city walls. It was precisely 75 years ago — Shivah Asar b’Tammuz of 1941 — that the rabbis of Vilna were arrested en masse, abused and tortured by the Nazi regime, and at day’s end, shot to death at Ponary — an isolated, deceptively bucolic expanse of farmland some five miles from the city. Vilna was perhaps Europe’s most vital center of Jewish scholarship and piety, dubbed “the Jerusalem of Lithuania” by no less a visitor than Napoleon. The Jewish national losses of Shivah Asar b’Tammuz 5701 were incalculable.

The executions at Ponary (also known as Ponarz, Punar, and Panarai) lasted for months, claiming thousands of victims. As many as 2,000 Jews were murdered on a single day. The lethal liquidation of Vilna Jewry began on July 4, 1941, as — a world away — Americans celebrated our independence for the last time before entering World War II.

The Sages of the Talmud taught: “Good things are destined to occur on historically auspicious days, while tragedies befall us on days with a history of misfortune” (Taanit 29A). By all accounts, the seventeenth of Tammuz is a day with an ambiguous legacy. In many ways it is an Independence Day to be celebrated with heartfelt gratitude as a watershed moment in the history of Jewish freedom, achievement, and opportunity. Yet the seventeenth of Tammuz also has a deeply dark record, comprising some of the most profound losses of both our distant past and our more recent history.

I fervently believe that the Prophet Zechariah was right. One day, even the darkest moments in our history will be transformed into joy and gladness and celebration. I fervently believe that the events of Shivah Asar b’Tammuz 5536 (July 4, 1776) represent a significant step forward in achieving such an enlightened and redeemed future. I also fervently believe that we as Jews — and we together with all Americans — have a great deal of work to do before the transformation envisioned by Zechariah can be realized fully.

I fervently believe that such a divine transformation can be brought about only through the concerted efforts of very human agents. The political and cultural divides in American society today represent a lamentable stain on the legacy of the founding fathers. The analogous infighting and petty partisan religious politics bedeviling the Jewish state and the Jewish people from within — despite the very real threats from increasingly hostile external detractors — make it clear that Shivah Asar b’Tammuz is no time to celebrate. Not yet.

It is a time to reflect on both our copious gifts and our considerable challenges. It is time to get to work. We occupy a moment in history at which both the United States and the House of Judah find ourselves at a crossroads. American Jews must take to heart our obligations both as citizens of the nation founded on Shivah Asar b’Tammuz and as heirs to an ancient and sacred tradition that met some of its most dire perils on Shivah Asar b’Tammuz.

I spent the first days of this historic month visiting Gettysburg, Pennsylvania. I was haunted there by the words of Abraham Lincoln, who (First Amendment objections notwithstanding) famously declared “a day of national humiliation, fasting and prayer” as the Civil War raged. Lincoln’s call for a day of fasting and reflection speaks to today’s Americans, who similarly must recognize the onerous cost of continued divisiveness. “Let us then rest humbly in the hope authorized by the Divine teachings, that the united cry of the Nation will be heard on high, and answered with blessings, no less than … the restoration of our now divided and suffering Country, to its former happy condition of unity and peace.” Fasting, prayer, and national introspection, together with the wise, principled, and effective discharge of our responsibilities as Jews and as Americans, still are very much the order of the day, lest painful breeches give way to a still more devastating calamity.

I write these words even as I fast in (an albeit delayed) observance of Shivah Asar b’Tammuz. We must begin this process in earnest. Now. Some obligations — unlike minor fast days — can simply not be put off until tomorrow.