diff --git a/js/webform.element.radios.js b/js/webform.element.radios.js
new file mode 100644
index 00000000..0c696754
--- /dev/null
+++ b/js/webform.element.radios.js
@@ -0,0 +1,58 @@
+/**
+ * @file
+ * Javascript behaviors for radio buttons.
+ *
+ * Fix #states and #required for radios buttons.
+ *
+ * @see Issue #2856795: If radio buttons are required but not filled form is nevertheless submitted.
+ * @see Issue #2856315: Conditional Logic - Requiring Radios in a Fieldset.
+ * @see Issue #2731991: Setting required on radios marks all options required.
+ * @see css/webform.form.css
+ * @see /core/misc/states.js
+ */
+
+(function ($, Drupal) {
+
+  'use strict';
+
+  /**
+   * Attach handler to add .js-webform-radios-fieldset to radios wrapper fieldset.
+   *
+   * @type {Drupal~behavior}
+   */
+  Drupal.behaviors.webformRadios = {
+    attach: function (context) {
+      $('.js-webform-radios', context).closest('fieldset.form-composite').addClass('js-webform-radios-fieldset');
+    }
+  };
+
+  // Make absolutely sure the below event handlers are triggered after
+  // the /core/misc/states.js event handlers by attaching them after DOM load.
+  $(function () {
+    Drupal.behaviors.webformRadios.attach($(document));
+
+    function setRequired($target, required) {
+      if (!$target.hasClass('js-webform-radios-fieldset')) {
+        return;
+      }
+
+      if (required) {
+        $target.find('input[type="radio"]').attr({'required': 'required', 'aria-required': 'aria-required'})
+        $target.find('legend span').addClass('js-form-required form-required');
+      }
+      else {
+        $target.find('input[type="radio"]').removeAttr('required aria-required');
+        $target.find('legend span').removeClass('js-form-required form-required');
+      }
+    }
+
+    setRequired($('.form-composite[required="required"]'), true);
+
+    $(document).on('state:required', function (e) {
+      if (e.trigger) {
+        setRequired($(e.target), e.value);
+      }
+    });
+  });
+
+})(jQuery, Drupal);
diff --git a/js/webform.states.js b/js/webform.states.js
index 3f7ab9e5..3fd4c12d 100644
--- a/js/webform.states.js
+++ b/js/webform.states.js
@@ -8,7 +8,7 @@
   'use strict';
 
   // Make absolutely sure the below event handlers are triggered after
-  // the state.js event handlers by attaching them after DOM load.
+  // the /core/misc/states.js event handlers by attaching them after DOM load.
   $(function () {
     var $document = $(document);
     $document.on('state:visible', function (e) {
diff --git a/src/Plugin/WebformElement/Radios.php b/src/Plugin/WebformElement/Radios.php
index 139abe33..07c7194f 100644
--- a/src/Plugin/WebformElement/Radios.php
+++ b/src/Plugin/WebformElement/Radios.php
@@ -2,6 +2,8 @@
 
 namespace Drupal\webform\Plugin\WebformElement;
 
+use Drupal\webform\WebformSubmissionInterface;
+
 /**
  * Provides a 'radios' element.
  *
@@ -25,4 +27,17 @@ class Radios extends OptionsBase {
     ];
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function prepare(array &$element, WebformSubmissionInterface $webform_submission) {
+    parent::prepare($element, $webform_submission);
+
+    // Issue #2856795: If radio buttons are required but not filled form is
+    // nevertheless submitted.
+    // Issue #2856315: Conditional Logic - Requiring Radios in a Fieldset.
+    $element['#attached']['library'][] = 'webform/webform.element.radios';
+  }
+
 }
+
diff --git a/src/Tests/Element/WebformElementOtherTest.php b/src/Tests/Element/WebformElementOtherTest.php
index 24e021c6..affed20f 100644
--- a/src/Tests/Element/WebformElementOtherTest.php
+++ b/src/Tests/Element/WebformElementOtherTest.php
@@ -76,7 +76,6 @@ class WebformElementOtherTest extends WebformTestBase {
     $this->assertRaw('<input data-drupal-selector="edit-radios-other-basic-other" type="text" id="edit-radios-other-basic-other" name="radios_other_basic[other]" value="Four" size="60" maxlength="128" placeholder="Enter other..." class="form-text" />');
 
     // Check advanced radios_other w/ custom label.
-    $this->assertRaw('<div id="edit-radios-other-advanced-radios" class="webform-options-display-two-columns form-radios">');
     $this->assertRaw('<label for="edit-radios-other-advanced" class="js-form-required form-required">Radios other advanced</label>');
     $this->assertRaw('<input data-drupal-selector="edit-radios-other-advanced-radios-other-" type="radio" id="edit-radios-other-advanced-radios-other-" name="radios_other_advanced[radios]" value="_other_" checked="checked" class="form-radio" />');
     $this->assertRaw('<input data-drupal-selector="edit-radios-other-advanced-other" aria-describedby="edit-radios-other-advanced-other--description" type="text" id="edit-radios-other-advanced-other" name="radios_other_advanced[other]" value="Four" size="60" maxlength="128" placeholder="What is this other option" class="form-text" />');
diff --git a/tests/modules/webform_test/config/install/webform.webform.test_element_radios.yml b/tests/modules/webform_test/config/install/webform.webform.test_element_radios.yml
new file mode 100644
index 00000000..5c36edaa
--- /dev/null
+++ b/tests/modules/webform_test/config/install/webform.webform.test_element_radios.yml
@@ -0,0 +1,153 @@
+langcode: en
+status: open
+dependencies:
+  enforced:
+    module:
+      - webform_test
+open: null
+close: null
+uid: null
+template: false
+id: test_element_radios
+title: 'Test: Element: Radios'
+description: 'Test the radios.'
+elements: |
+  radios_required_example:
+    '#type': details
+    '#title': 'Radios required'
+    '#open': true
+    radios_required:
+      '#type': radios
+      '#title': radios_required
+      '#required': true
+      '#options': yes_no
+  radios_required_conditional_example:
+    '#type': details
+    '#title': 'Radios required conditional'
+    '#open': true
+    radios_required_conditional_trigger:
+      '#type': checkbox
+      '#title': 'Required the below radio button'
+      '#default_value': true
+    radios_required_conditional:
+      '#type': radios
+      '#title': radios_required
+      '#options': yes_no
+      '#states':
+        required:
+          ':input[name="radios_required_conditional_trigger"]':
+            checked: true
+  buttons_required_conditional_example:
+    '#type': details
+    '#title': 'Buttons required conditional'
+    '#open': true
+    buttons_required_conditional_trigger:
+      '#type': checkbox
+      '#title': 'Required the below buttons'
+      '#default_value': true
+    buttons_required_conditional:
+      '#type': webform_buttons
+      '#title': buttons_required
+      '#options': yes_no
+      '#states':
+        required:
+          ':input[name="buttons_required_conditional_trigger"]':
+            checked: true
+css: ''
+javascript: ''
+settings:
+  page: true
+  page_submit_path: ''
+  page_confirm_path: ''
+  form_submit_label: ''
+  form_submit_once: false
+  form_submit_attributes: {  }
+  form_exception_message: ''
+  form_closed_message: ''
+  form_previous_submissions: true
+  form_confidential: false
+  form_confidential_message: ''
+  form_prepopulate: false
+  form_prepopulate_source_entity: false
+  form_disable_autocomplete: false
+  form_novalidate: false
+  form_unsaved: false
+  form_disable_back: false
+  form_autofocus: false
+  form_details_toggle: false
+  wizard_progress_bar: true
+  wizard_progress_pages: false
+  wizard_progress_percentage: false
+  wizard_next_button_label: ''
+  wizard_next_button_attributes: {  }
+  wizard_prev_button_label: ''
+  wizard_prev_button_attributes: {  }
+  wizard_start_label: ''
+  wizard_complete: true
+  wizard_complete_label: ''
+  preview: 0
+  preview_next_button_label: ''
+  preview_next_button_attributes: {  }
+  preview_prev_button_label: ''
+  preview_prev_button_attributes: {  }
+  preview_message: ''
+  draft: false
+  draft_auto_save: false
+  draft_button_label: ''
+  draft_button_attributes: {  }
+  draft_saved_message: ''
+  draft_loaded_message: ''
+  confirmation_type: message
+  confirmation_title: ''
+  confirmation_message: ''
+  confirmation_url: ''
+  confirmation_attributes: {  }
+  confirmation_back: true
+  confirmation_back_label: ''
+  confirmation_back_attributes: {  }
+  limit_total: null
+  limit_total_message: ''
+  limit_user: null
+  limit_user_message: ''
+  purge: none
+  purge_days: null
+  entity_limit_total: null
+  entity_limit_user: null
+  results_disabled: true
+  results_disabled_ignore: false
+  token_update: false
+access:
+  create:
+    roles:
+      - anonymous
+      - authenticated
+    users: {  }
+  view_any:
+    roles: {  }
+    users: {  }
+  update_any:
+    roles: {  }
+    users: {  }
+  delete_any:
+    roles: {  }
+    users: {  }
+  purge_any:
+    roles: {  }
+    users: {  }
+  view_own:
+    roles: {  }
+    users: {  }
+  update_own:
+    roles: {  }
+    users: {  }
+  delete_own:
+    roles: {  }
+    users: {  }
+handlers:
+  debug:
+    id: debug
+    label: Debug
+    handler_id: debug
+    status: true
+    weight: 1
+    settings: {  }
diff --git a/webform.libraries.yml b/webform.libraries.yml
index b833e3c4..0856e74e 100644
--- a/webform.libraries.yml
+++ b/webform.libraries.yml
@@ -390,6 +390,15 @@ webform.element.other:
     - core/jquery
     - core/jquery.once
 
+webform.element.radios:
+  version: VERSION
+  js:
+    js/webform.element.radios.js: {}
+  dependencies:
+    - core/drupal
+    - core/jquery
+    - core/jquery.once
+
 webform.element.range:
   version: VERSION
   css:
diff --git a/webform.module b/webform.module
index 4773eea4..fb63522c 100644
--- a/webform.module
+++ b/webform.module
@@ -587,7 +587,6 @@ function webform_theme_suggestions_alter(array &$suggestions, array $variables,
     $suggestions[] = $hook . '__' . $webform->id();
   }
 }
-
 /**
  * Prepares variables for checkboxes templates.
  *
@@ -607,6 +606,8 @@ function webform_preprocess_checkboxes(&$variables) {
  */
 function webform_preprocess_radios(&$variables) {
   webform_preprocess_checkboxes($variables);
+  // @see js/webform.element.radios.js
+  $variables['attributes']['class'][] = 'js-webform-radios';
 }
 
 /**