The warning signs came early this season, Jewish-themed post cards with veiled messianic references arriving in mailboxes throughout the Brighton Beach neighborhood.

Friends tell me they get a knock on their door from people wearing a Star of David and a kipa who want to talk with them. These are Jews for Jesus missionaries, and they are a regular summer fixture in South Brooklyn’s Jewish neighborhoods. But what’s especially worrisome is that they now include some local young Russian Jews among their ranks; the number of Jews for Jesus missionaries appear to be growing, and their tactics appear to be getting more sophisticated.

It is easy to direct our anger at the missionaries, to give in to the knee-jerk reaction of, “Let’s go out there and tell people that these missionaries are not ‘real Jews.’” Debating with them may be emotionally satisfying at times, but it usually is counterproductive, creating sympathy where bewilderment would otherwise dominate.

As a Jew, a proud Russian Jew, I’m sad, but I’m not angry with the missionaries. They are sincere in their beliefs. They tend to be kind, well mannered, passionate and truly caring. They are also harmless to educated Jews.

What is striking is that the missionaries, many of them from another part of the country, seem to care more about the future and beliefs of my fellow Russian Jews than the Jews of the vast and diverse Jewish communities of New York. Unless something changes — unless our common sense of Jewish peoplehood is strengthened and Jews begin to truly care, not just about their own insular communities, but about the Jewish future of those who are most in danger of drifting way — it’s inevitable that the missionaries will be successful.

It will not be dramatic, it will take a few generations, but without Jewish education, it is certain that those descendants of Russian Jews who practice a religion will most likely not be practicing Judaism. This is not a wild, alarmist speculation. It is simply a fact of Jewish history. It is not unique to Russian Jews. It is the fate of all who drift away from the tribe, the great grandchildren of those who didn’t get a Jewish education, whose bonds of ethnicity faded into intermarriage and assimilation.

A generation ago, the American Jewish community came together to help free Soviet Jewry. It was a proud moment for the Jewish people, when passion overcame apathy. We rallied together for a just cause and made history. Today, an estimated 752,000 Russian Jews live in North America, and they make up the largest single ethnic group of unaffiliated Jews, and the Jewish community’s largest opportunity, as well. About 216,000 are in New York, and the vast majority of them live in the predominantly Russian neighborhoods of South Brooklyn. How ironic that they and their parents were freed as Soviet Jews, but risk being lost as American Jews.

For the lucky few like me who benefited from a Jewish day school education, the foundations of Jewish identity are strong enough to ensure a Jewish future for our children. And for the 11 percent of all 18- to 30-year-old Russian Jews in the New York area who, over the past seven years, were fortunate enough to complete the RAJE (Russian American Jewish Experience) Fellowship and Israel trip program, with 250 hours of Jewish educational engagement, the missionaries are not much of a threat. These RAJE alumni, and people involved in organizations like COJECO (the Council of Jewish Émigré Community Organizations), are too busy being involved in Jewish organizations and building their own Jewish future. Sadly, for their peers who are turned away from the program each semester, due to lack of funding, the answer is uncertain.

When Superstorm Sandy devastated our center and so many other local synagogues last fall, I imagined that a vulnerable Jewish community, in the heart of New York and under siege by missionaries, would surely draw the attention of Jewish communal and philanthropic leaders. After all, more than half of the people in the neighborhoods of Brighton Beach and Sheepshead Bay are Jewish; it’s the highest concentration of unaffiliated Russian Jews anywhere in the diaspora. Surely rebuilding the Jewish communal infrastructure serving such a community would be seen as a natural priority in ensuring that young Jews would have a place to gather and experience Jewish life. It was a sober reality check when little such support materialized.

Some help did arrive; at a meeting in City Hall, I met the Rev. Daniel Delgado, whose organization, Third Day Missions, focuses on long-term post Sandy rebuilding projects. Over the summer months, churches from across the country were rallied to send groups of volunteers who have helped clean, de-mold, put on sheetrock and paint. These Christian volunteers are wonderful people; they respect our traditions and are not there to proselytize. On a human level, it is heartwarming to see their dedication and kind-hearted sincerity. We are truly grateful to them. But deep inside, as a Jew, my heart cries out: can we build a partnership for a Jewish future, or does the future belong to the missionaries?

Rabbi Mordechai Tokarsky is the co-founder and director of RAJE (Russian American Jewish Experience), in Brooklyn.