diff --git a/preprocessing.py b/preprocessing.py
index 595db3890..bd02da120 100644
--- a/preprocessing.py
+++ b/preprocessing.py
@@ -262,6 +262,40 @@ def get_tpu_bt_input_tensors(games, games_nr, batch_size, num_repeats=1,
     return dataset
 
 
+def get_many_tpu_bt_input_tensors(games, games_nr, batch_size,
+                                  start_at, num_datasets,
+                                  moves=2**21,
+                                  window_size=500e3,
+                                  window_increment=25000):
+    dataset = None
+    for i in range(num_datasets):
+        # TODO(amj) mixin calibration games with some math. (from start_at that
+        # is proportionally along compared to last_game_number?  comparing
+        # timestamps?)
+        ds = games.moves_from_games(start_at + (i * window_increment),
+                                    start_at + (i * window_increment) + window_size,
+                                    moves=moves,
+                                    shuffle=True,
+                                    column_family=bigtable_input.TFEXAMPLE,
+                                    column='example')
+        dataset = dataset.concatenate(ds) if dataset else ds
+
+    dataset = dataset.repeat(1)
+    dataset = dataset.map(lambda row_name, s: s)
+    dataset = dataset.batch(batch_size,drop_remainder=False)
+    dataset = dataset.map(
+        functools.partial(batch_parse_tf_example, batch_size))
+    # Unbatch the dataset so we can rotate it
+    dataset = dataset.apply(tf.contrib.data.unbatch())
+    dataset = dataset.apply(tf.contrib.data.map_and_batch(
+        _random_rotation_pure_tf,
+        batch_size,
+        drop_remainder=True))
+
+    dataset = dataset.prefetch(tf.contrib.data.AUTOTUNE)
+    return dataset
+
+
 def make_dataset_from_selfplay(data_extracts):
     """
     Returns an iterable of tf.Examples.
diff --git a/train.py b/train.py
index d6b24bcfe..e6300e2f5 100644
--- a/train.py
+++ b/train.py
@@ -54,6 +54,15 @@
 flags.DEFINE_bool('freeze', False,
                   'Whether to freeze the graph at the end of training.')
 
+flags.DEFINE_bool('train_many', False,
+                  'Whether to run train repeatedly, automatically incrementing the window')
+
+flags.DEFINE_integer('window_start_at', 10000000,
+                     'Used with `train_many`.  The game number where the window begins')
+
+flags.DEFINE_integer('num_datasets', 3,
+                     'Used with `train_many`. The number of times to increment the window and re-train.')
+
 
 flags.register_multi_flags_validator(
     ['use_bt', 'use_tpu'],
@@ -139,6 +148,39 @@ def after_run(self, run_context, run_values):
             self.before_weights = None
 
 
+def train_many(start_at=1000000, num_datasets=3, moves=2**24):
+    """ Trains on a set of bt_datasets, skipping eval for now.
+    (from preprocessing.get_many_tpu_bt_input_tensors)
+    """
+    if not FLAGS.use_tpu and FLAGS.use_bt:
+        raise ValueError("Only tpu & bt mode supported")
+
+    tf.logging.set_verbosity(tf.logging.INFO)
+    estimator = dual_net.get_estimator()
+    effective_batch_size = FLAGS.train_batch_size * FLAGS.num_tpu_cores
+
+    def _input_fn(params):
+        games = bigtable_input.GameQueue(
+            FLAGS.cbt_project, FLAGS.cbt_instance, FLAGS.cbt_table)
+        games_nr = bigtable_input.GameQueue(
+            FLAGS.cbt_project, FLAGS.cbt_instance, FLAGS.cbt_table + '-nr')
+
+        return preprocessing.get_many_tpu_bt_input_tensors(
+            games, games_nr, params['batch_size'],
+            moves=moves,
+            window_size=FLAGS.window_size,
+            start_at=start_at, num_datasets=num_datasets)
+
+    hooks = []
+
+    steps = num_datasets * FLAGS.steps_to_train
+    logging.info("Training, steps = %s, batch = %s -> %s examples",
+                 steps or '?', effective_batch_size,
+                 (steps * effective_batch_size) if steps else '?')
+
+    estimator.train(_input_fn, steps=steps, hooks=hooks)
+
+
 def train(*tf_records: "Records to train on"):
     """Train on examples."""
     tf.logging.set_verbosity(tf.logging.INFO)
@@ -209,11 +251,15 @@ def _input_fn():
 
 def main(argv):
     """Train on examples and export the updated model weights."""
-    tf_records = argv[1:]
-    logging.info("Training on %s records: %s to %s",
-                 len(tf_records), tf_records[0], tf_records[-1])
-    with utils.logged_timer("Training"):
-        train(*tf_records)
+    if FLAGS.train_many:
+      with utils.logged_timer("Training"):
+        train_many(FLAGS.window_start_at, FLAGS.num_datasets)
+    else:
+      tf_records = argv[1:]
+      logging.info("Training on %s records: %s to %s",
+                   len(tf_records), tf_records[0], tf_records[-1])
+      with utils.logged_timer("Training"):
+          train(*tf_records)
     if FLAGS.export_path:
         dual_net.export_model(FLAGS.export_path)
     if FLAGS.freeze: