diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..280e625
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/core_software
diff --git a/fetch_externals.py b/fetch_externals.py
new file mode 100755
index 0000000..5759bfb
--- /dev/null
+++ b/fetch_externals.py
@@ -0,0 +1,100 @@
+#!/usr/bin/env python
+
+#
+# Copyright (c) 2019-2020 Arm Limited. All rights reserved.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the License); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an AS IS BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import os
+import subprocess
+
+def print_args(args, **kwargs):
+    cwd = kwargs['cwd']
+
+    if isinstance(args, list):
+        args = ' '.join(args)
+
+    print('%s$ %s' % (cwd, args))
+
+def check_call(args, **kwargs):
+    print_args(args, **kwargs)
+    return subprocess.check_call(args, **kwargs)
+
+def check_output(args, **kwargs):
+    print_args(args, **kwargs)
+    return subprocess.check_output(args, **kwargs)
+
+class Git(object):
+    def __init__(self, path, fetchurl, pushurl=None, revision='origin/master'):
+        self.path = path
+        self.fetchurl = fetchurl
+        self.pushurl = pushurl
+        self.revision = revision
+
+    def init(self):
+        if not os.path.exists(self.path):
+            os.makedirs(self.path)
+
+        if not os.path.exists(os.path.join(self.path, '.git')):
+            check_output(['git', 'init'], cwd=self.path)
+
+    def remote_add(self, name, fetchurl):
+        remotes = check_output(['git', 'remote'], cwd=self.path).decode('utf-8').split('\n')
+        if not name in remotes:
+            check_output(['git', 'remote', 'add', '-m', self.revision, name, self.fetchurl], cwd=self.path)
+
+            if self.pushurl:
+                check_output(['git', 'remote', 'set-url', '--add', '--push', name, self.pushurl], cwd=self.path)
+
+    def fetch(self):
+        check_output(['git', 'fetch'], cwd=self.path)
+
+    def checkout(self, revision):
+        rev = self.__get_rev(revision)
+        check_output(['git', 'checkout', rev], stderr=subprocess.STDOUT, cwd=self.path)
+
+    def clone(self):
+        if not os.path.exists(os.path.join(self.path, '.git')):
+            self.init()
+            self.remote_add('origin', self.fetchurl)
+            self.fetch()
+            self.checkout(self.revision)
+
+    def rebase(self):
+        rev = self.__get_rev(self.revision)
+        check_output(['git', 'rebase', rev], cwd=self.path)
+
+    def __get_rev(self, revision):
+        try:
+            rev = check_output(['git', 'rev-parse', 'origin/' + self.revision], cwd=self.path)
+        except:
+            rev = check_output(['git', 'rev-parse', self.revision], cwd=self.path)
+
+        return rev.decode('utf-8').strip()
+
+basedir = os.path.dirname(os.path.realpath(__file__))
+
+externals = [
+    Git(os.path.join(basedir, 'core_software'), 'ssh://review.mlplatform.org:29418/ml/ethos-u/ethos-u-core-software', revision='master'),
+    Git(os.path.join(basedir, 'core_software/core_driver'), 'ssh://review.mlplatform.org:29418/ml/ethos-u/ethos-u-core-driver', revision='master'),
+    Git(os.path.join(basedir, 'core_software/cmsis'), 'https://github.com/ARM-software/CMSIS_5.git', revision='master'),
+    Git(os.path.join(basedir, 'core_software/tensorflow'), 'https://github.com/tensorflow/tensorflow', revision='master'),
+]
+
+for external in externals:
+    external.clone()
+    external.fetch()
+    external.rebase()