How 9/11 transformed synagogue security into a new reality for the Jewish community

At sundown on Friday, Sept. 11, as America marks 25 years since the terrorist attacks that killed nearly 3,000 people, Jewish families across the country will welcome in Rosh Hashanah, the Jewish new year marking 5787.

They will enter synagogues at the moment of peak annual attendance, walking past armed guards, security cameras, secured doors and bag checks.

The convergence brings into focus how the Sept. 11 attacks transformed security in American synagogues and helped create the...