WordPress Apply new category to all existing posts

functions.php

add_action( 'init', 'update_taxonomy');
function update_taxonomy() {

  $posts = get_posts(
    array(
      'post_type' => 'post',
      'posts_per_page' => -1
    )
  );

  // where 134 is new category ID
  foreach ($posts as $post) {
    wp_set_object_terms($post->ID, 134, 'category', true);
  }
}