diff --git a/core/modules/forum/forum.libraries.yml b/core/modules/forum/forum.libraries.yml
index bf7079e..7e75c49 100644
--- a/core/modules/forum/forum.libraries.yml
+++ b/core/modules/forum/forum.libraries.yml
@@ -3,3 +3,26 @@ forum.index:
   css:
     component:
       css/forum.theme.css: {}
+
+drupal.forum-topic-new-indicator:
+  version: VERSION
+  js:
+    js/forum-topic-new-indicator: {}
+    dependencies:
+      - core/jquery
+      - core/jquery.once
+      - core/drupal
+      - history/api
+      - core/drupal.displace
+
+drupal.forum-reply-new-indicator:
+  version: VERSION
+  js:
+    js/forum-reply-new-indicator: {}
+    dependencies:
+      - core/jquery
+      - core/jquery.once
+      - core/drupal
+      - history/api
+      - core/drupal.displace
+
diff --git a/core/modules/forum/js/forum-reply-new-indicator.js b/core/modules/forum/js/forum-reply-new-indicator.js
new file mode 100644
index 0000000..49b2c4f
--- /dev/null
+++ b/core/modules/forum/js/forum-reply-new-indicator.js
@@ -0,0 +1,26 @@
+/**
+ * Attaches behaviors for a forum topic's "new replies" indicator on /forum/%tid.
+ *
+ * May only be loaded for authenticated users, with the History module
+ * installed.
+ */
+(function ($, Drupal, window) {
+
+  "use strict";
+
+  /**
+   * Render "new replies" indicators wherever necessary.
+   */
+  Drupal.behaviors.forumReplyNewIndicator = {
+    attach: function (context) {
+      // Collect all "new replies" forum indicator placeholders (and their corresponding
+      // node IDs)
+      var nodeIDs = [];
+      var $placeholders = $(context)
+        .find('[data-forum-reply-timestamp]')
+        .once('history')
+        .filter(function () {
+          var $placeholder = $(this);
+          var forumTimestamp = parseInt($placeholder.attr('data-forum-topic-timestamp'), 10);
+
+  }
diff --git a/core/modules/forum/js/forum-topic-new-indicator.js b/core/modules/forum/js/forum-topic-new-indicator.js
new file mode 100644
index 0000000..f3d081a
--- /dev/null
+++ b/core/modules/forum/js/forum-topic-new-indicator.js
@@ -0,0 +1,26 @@
+/**
+ * Attaches behaviors for the Forum module's "new topics" indicator on /forum.
+ *
+ * May only be loaded for authenticated users, with the History module
+ * installed.
+ */
+(function ($, Drupal, window) {
+
+  "use strict";
+
+  /**
+   * Render "new topics" indicators wherever necessary.
+   */
+  Drupal.behaviors.forumTopicNewIndicator = {
+    attach: function (context) {
+      // Collect all "new topics" forum indicator placeholders (and their corresponding
+      // node IDs)
+      var nodeIDs = [];
+      var $placeholders = $(context)
+        .find('[data-forum-topic-timestamp]')
+        .once('history')
+        .filter(function () {
+          var $placeholder = $(this);
+          var forumTimestamp = parseInt($placeholder.attr('data-forum-topic-timestamp'), 10);
+
+  }