diff --git a/lib/class-wp-rest-menu-items-controller.php b/lib/class-wp-rest-menu-items-controller.php
index 8329e8772220e..2e82b5337d65d 100644
--- a/lib/class-wp-rest-menu-items-controller.php
+++ b/lib/class-wp-rest-menu-items-controller.php
@@ -410,7 +410,7 @@ protected function prepare_item_for_database( $request ) {
 				'menu-item-object-id'   => 0,
 				'menu-item-object'      => '',
 				'menu-item-parent-id'   => 0,
-				'menu-item-position'    => 0,
+				'menu-item-position'    => 1,
 				'menu-item-type'        => 'custom',
 				'menu-item-title'       => '',
 				'menu-item-url'         => '',
@@ -524,51 +524,6 @@ protected function prepare_item_for_database( $request ) {
 			}
 		}
 
-		// If menu id is set, valid the value of menu item position and parent id.
-		if ( ! empty( $prepared_nav_item['menu-id'] ) ) {
-			// Check if nav menu is valid.
-			if ( ! is_nav_menu( $prepared_nav_item['menu-id'] ) ) {
-				return new WP_Error( 'invalid_menu_id', __( 'Invalid menu ID.', 'gutenberg' ), array( 'status' => 400 ) );
-			}
-
-			// If menu item position is set to 0, insert as the last item in the existing menu.
-			$menu_items = wp_get_nav_menu_items( $prepared_nav_item['menu-id'], array( 'post_status' => 'publish,draft' ) );
-			if ( 0 === (int) $prepared_nav_item['menu-item-position'] ) {
-				if ( $menu_items ) {
-					$last_item = $menu_items[ count( $menu_items ) - 1 ];
-					if ( $last_item && isset( $last_item->menu_order ) ) {
-						$prepared_nav_item['menu-item-position'] = $last_item->menu_order + 1;
-					} else {
-						$prepared_nav_item['menu-item-position'] = count( $menu_items ) - 1;
-					}
-					array_push( $menu_items, $last_item );
-				} else {
-					$prepared_nav_item['menu-item-position'] = 1;
-				}
-			}
-
-			// Check if existing menu position is already in use by another menu item.
-			$menu_item_ids = array();
-			foreach ( $menu_items as $menu_item ) {
-				$menu_item_ids[] = $menu_item->ID;
-				if ( $menu_item->ID !== (int) $menu_item_db_id ) {
-					if ( (int) $prepared_nav_item['menu-item-position'] === (int) $menu_item->menu_order ) {
-						return new WP_Error( 'invalid_menu_order', __( 'Invalid menu position.', 'gutenberg' ), array( 'status' => 400 ) );
-					}
-				}
-			}
-
-			// Check if valid parent id is valid nav menu item in menu.
-			if ( $prepared_nav_item['menu-item-parent-id'] ) {
-				if ( ! is_nav_menu_item( $prepared_nav_item['menu-item-parent-id'] ) ) {
-					return new WP_Error( 'invalid_menu_item_parent', __( 'Invalid menu item parent.', 'gutenberg' ), array( 'status' => 400 ) );
-				}
-				if ( ! $menu_item_ids || ! in_array( $prepared_nav_item['menu-item-parent-id'], $menu_item_ids, true ) ) {
-					return new WP_Error( 'invalid_item_parent', __( 'Invalid menu item parent.', 'gutenberg' ), array( 'status' => 400 ) );
-				}
-			}
-		}
-
 		foreach ( array( 'menu-item-object-id', 'menu-item-parent-id' ) as $key ) {
 			// Note we need to allow negative-integer IDs for previewed objects not inserted yet.
 			$prepared_nav_item[ $key ] = (int) $prepared_nav_item[ $key ];
@@ -750,8 +705,13 @@ public function prepare_item_for_response( $post, $request ) {
 			$base = ! empty( $taxonomy->rest_base ) ? $taxonomy->rest_base : $taxonomy->name;
 
 			if ( rest_is_field_included( $base, $fields ) ) {
-				$terms         = get_the_terms( $post, $taxonomy->name );
-				$data[ $base ] = $terms ? array_values( wp_list_pluck( $terms, 'term_id' ) ) : array();
+				$terms    = get_the_terms( $post, $taxonomy->name );
+				$term_ids = $terms ? array_values( wp_list_pluck( $terms, 'term_id' ) ) : array();
+				if ( 'nav_menu' === $taxonomy->name ) {
+					$data[ $base ] = $term_ids ? array_shift( $term_ids ) : 0;
+				} else {
+					$data[ $base ] = $term_ids;
+				}
 			}
 		}
 
@@ -962,10 +922,11 @@ public function get_item_schema() {
 			'description' => __( 'The DB ID of the nav_menu_item that is this item\'s menu parent, if any, otherwise 0.', 'gutenberg' ),
 			'context'     => array( 'view', 'edit', 'embed' ),
 			'type'        => 'integer',
-			'minimum'     => 0,
-			'default'     => 0,
+			'minimum'     => 1,
+			'default'     => 1,
 		);
-		$schema['properties']['object']     = array(
+
+		$schema['properties']['object'] = array(
 			'description' => __( 'The type of object originally represented, such as "category," "post", or "attachment."', 'gutenberg' ),
 			'context'     => array( 'view', 'edit', 'embed' ),
 			'type'        => 'string',
diff --git a/packages/edit-navigation/src/store/actions.js b/packages/edit-navigation/src/store/actions.js
index 91b2cc7500197..0eb641a12858f 100644
--- a/packages/edit-navigation/src/store/actions.js
+++ b/packages/edit-navigation/src/store/actions.js
@@ -65,7 +65,7 @@ export const createMissingMenuItems = serializeProcessing( function* ( post ) {
 				data: {
 					title: 'Placeholder',
 					url: 'Placeholder',
-					menu_order: 0,
+					menu_order: 1,
 				},
 			} );
 
diff --git a/packages/edit-navigation/src/store/test/actions.js b/packages/edit-navigation/src/store/test/actions.js
index 0c2bf7c90f681..fc5ca7f5c4a65 100644
--- a/packages/edit-navigation/src/store/test/actions.js
+++ b/packages/edit-navigation/src/store/test/actions.js
@@ -77,7 +77,7 @@ describe( 'createMissingMenuItems', () => {
 				data: {
 					title: 'Placeholder',
 					url: 'Placeholder',
-					menu_order: 0,
+					menu_order: 1,
 				},
 			} )
 		);
@@ -200,7 +200,7 @@ describe( 'createMissingMenuItems', () => {
 				data: {
 					title: 'Placeholder',
 					url: 'Placeholder',
-					menu_order: 0,
+					menu_order: 1,
 				},
 			} )
 		);
diff --git a/phpunit/class-rest-nav-menu-items-controller-test.php b/phpunit/class-rest-nav-menu-items-controller-test.php
index 34dd004e162fe..46c55d17653ec 100644
--- a/phpunit/class-rest-nav-menu-items-controller-test.php
+++ b/phpunit/class-rest-nav-menu-items-controller-test.php
@@ -277,39 +277,47 @@ public function test_create_item_invalid_term() {
 	public function test_create_item_change_position() {
 		wp_set_current_user( self::$admin_id );
 		$new_menu_id = wp_create_nav_menu( rand_str() );
+		$expected    = array();
+		$actual      = array();
 		for ( $i = 1; $i < 5; $i ++ ) {
 			$request = new WP_REST_Request( 'POST', '/__experimental/menu-items' );
 			$request->add_header( 'content-type', 'application/x-www-form-urlencoded' );
 			$params = $this->set_menu_item_data(
 				array(
-					'menus' => $new_menu_id,
+					'menu_order' => $i,
+					'menus'      => $new_menu_id,
 				)
 			);
 			$request->set_body_params( $params );
 			$response = rest_get_server()->dispatch( $request );
 			$this->check_create_menu_item_response( $response );
 			$data = $response->get_data();
-			$this->assertEquals( $data['menu_order'], $i );
+
+			$expected[] = $i;
+			$actual[]   = $data['menu_order'];
 		}
+		$this->assertEquals( $actual, $expected );
 	}
 
 	/**
 	 *
 	 */
-	public function test_create_item_invalid_position() {
+	public function test_menu_order_must_be_set() {
 		wp_set_current_user( self::$admin_id );
 		$new_menu_id = wp_create_nav_menu( rand_str() );
-		$request     = new WP_REST_Request( 'POST', '/__experimental/menu-items' );
+
+		$request = new WP_REST_Request( 'POST', '/__experimental/menu-items' );
 		$request->add_header( 'content-type', 'application/x-www-form-urlencoded' );
 		$params = $this->set_menu_item_data(
 			array(
-				'menu_order' => 1,
+				'menu_order' => 0,
 				'menus'      => $new_menu_id,
 			)
 		);
 		$request->set_body_params( $params );
 		$response = rest_get_server()->dispatch( $request );
-		$this->check_create_menu_item_response( $response );
+		$this->assertErrorResponse( 'rest_invalid_param', $response, 400 );
+
 		$request = new WP_REST_Request( 'POST', '/__experimental/menu-items' );
 		$request->add_header( 'content-type', 'application/x-www-form-urlencoded' );
 		$params = $this->set_menu_item_data(
@@ -320,8 +328,7 @@ public function test_create_item_invalid_position() {
 		);
 		$request->set_body_params( $params );
 		$response = rest_get_server()->dispatch( $request );
-
-		$this->assertErrorResponse( 'invalid_menu_order', $response, 400 );
+		$this->assertEquals( 201, $response->get_status() );
 	}
 
 	/**
@@ -380,43 +387,6 @@ public function test_create_item_invalid_parent() {
 		$this->assertErrorResponse( 'rest_invalid_param', $response, 400 );
 	}
 
-	/**
-	 *
-	 */
-	public function test_create_item_invalid_parent_menu_item() {
-		wp_set_current_user( self::$admin_id );
-		$new_menu_id = wp_create_nav_menu( rand_str() );
-		$request     = new WP_REST_Request( 'POST', '/__experimental/menu-items' );
-		$request->add_header( 'content-type', 'application/x-www-form-urlencoded' );
-		$params = $this->set_menu_item_data(
-			array(
-				'menus'  => $new_menu_id,
-				'parent' => $this->menu_item_id,
-			)
-		);
-		$request->set_body_params( $params );
-		$response = rest_get_server()->dispatch( $request );
-		$this->assertErrorResponse( 'invalid_item_parent', $response, 400 );
-	}
-
-	/**
-	 *
-	 */
-	public function test_create_item_invalid_parent_post() {
-		wp_set_current_user( self::$admin_id );
-		$post_id = self::factory()->post->create();
-		$request = new WP_REST_Request( 'POST', '/__experimental/menu-items' );
-		$request->add_header( 'content-type', 'application/x-www-form-urlencoded' );
-		$params = $this->set_menu_item_data(
-			array(
-				'parent' => $post_id,
-			)
-		);
-		$request->set_body_params( $params );
-		$response = rest_get_server()->dispatch( $request );
-		$this->assertErrorResponse( 'invalid_menu_item_parent', $response, 400 );
-	}
-
 	/**
 	 *
 	 */
@@ -830,8 +800,13 @@ protected function check_menu_item_data( $post, $data, $context, $links ) {
 			$this->assertTrue( isset( $data[ $taxonomy->rest_base ] ) );
 			$terms = wp_get_object_terms( $post->ID, $taxonomy->name, array( 'fields' => 'ids' ) );
 			sort( $terms );
-			sort( $data[ $taxonomy->rest_base ] );
-			$this->assertEquals( $terms, $data[ $taxonomy->rest_base ] );
+			if ( 'nav_menu' === $taxonomy->name ) {
+				$term_id = $terms ? array_shift( $terms ) : 0;
+				$this->assertEquals( $term_id, $data[ $taxonomy->rest_base ] );
+			} else {
+				sort( $data[ $taxonomy->rest_base ] );
+				$this->assertEquals( $terms, $data[ $taxonomy->rest_base ] );
+			}
 		}
 
 		// test links.
@@ -908,7 +883,7 @@ protected function set_menu_item_data( $args = array() ) {
 		$defaults = array(
 			'object_id'   => 0,
 			'parent'      => 0,
-			'menu_order'  => 0,
+			'menu_order'  => 1,
 			'menus'       => $this->menu_id,
 			'type'        => 'custom',
 			'title'       => 'Custom Link Title',