Birkat Hamazon's first three blessings are old, generally dated to the Second Temple period and structured, according to rabbinic tradition, by different biblical figures and later sages at different points, but the fourth blessing, HaTov VeHaMeitiv, praising God as the one who is good and does good, was added considerably later, and the Talmud itself, in tractate Berakhot, connects its addition specifically to the aftermath of the Bar Kokhba revolt against Rome, crushed in 135 CE, and to the Roman authorities' eventual grant of permission for the bodies of the fallen defenders of Beitar to be buried, after having reportedly been left exposed for a considerable period following the revolt's defeat, an event the rabbis treated as itself warranting a blessing of gratitude despite the surrounding catastrophe.
This fourth blessing's origin story means the grace after meals, recited after every substantial meal by observant Jews to this day, carries within its fixed liturgical structure a specific commemorative layer added in direct historical response to a national military and religious catastrophe, quite unlike the biblically derived obligation and content of the first three blessings, so a single prayer recited daily for entirely different, food related reasons also functions, in its final section, as an embedded historical memorial to a specific defeat and its grim aftermath nearly two thousand years ago, a layering of everyday ritual obligation and historical commemoration characteristic of how rabbinic liturgy often absorbed historical memory into ordinary recurring prayer rather than setting it apart in separate commemorative texts.