diff --git a/dulwich/cli.py b/dulwich/cli.py
index 38b805f0c..4ccf991c6 100755
--- a/dulwich/cli.py
+++ b/dulwich/cli.py
@@ -34,7 +34,7 @@
 import argparse
 import optparse
 import signal
-from typing import Dict, Type
+from typing import Dict, Type, Optional
 
 from dulwich import porcelain
 from dulwich.client import get_transport_and_path
@@ -321,14 +321,6 @@ def run(self, args):
         porcelain.rev_list(".", args)
 
 
-class cmd_submodule(Command):
-    def run(self, args):
-        parser = optparse.OptionParser()
-        options, args = parser.parse_args(args)
-        for path, sha in porcelain.submodule_list("."):
-            sys.stdout.write(' %s %s\n' % (sha, path))
-
-
 class cmd_tag(Command):
     def run(self, args):
         parser = optparse.OptionParser()
@@ -581,10 +573,11 @@ def run(self, args):
 
 class SuperCommand(Command):
 
-    subcommands = {}  # type: Dict[str, Type[Command]]
+    subcommands: Dict[str, Type[Command]] = {}
+    default_command: Optional[Type[Command]] = None
 
     def run(self, args):
-        if not args:
+        if not args and not self.default_command:
             print("Supported subcommands: %s" % ", ".join(self.subcommands.keys()))
             return False
         cmd = args[0]
@@ -603,6 +596,30 @@ class cmd_remote(SuperCommand):
     }
 
 
+class cmd_submodule_list(Command):
+    def run(self, argv):
+        parser = argparse.ArgumentParser()
+        parser.parse_args(argv)
+        for path, sha in porcelain.submodule_list("."):
+            sys.stdout.write(' %s %s\n' % (sha, path))
+
+
+class cmd_submodule_init(Command):
+    def run(self, argv):
+        parser = argparse.ArgumentParser()
+        parser.parse_args(argv)
+        porcelain.submodule_init(".")
+
+
+class cmd_submodule(SuperCommand):
+
+    subcommands = {
+        "init": cmd_submodule_init,
+    }
+
+    default_command = cmd_submodule_init
+
+
 class cmd_check_ignore(Command):
     def run(self, args):
         parser = optparse.OptionParser()
diff --git a/dulwich/config.py b/dulwich/config.py
index 7f09ae57a..857ef520b 100644
--- a/dulwich/config.py
+++ b/dulwich/config.py
@@ -750,6 +750,12 @@ def sections(self) -> Iterator[Section]:
                     yield section
 
 
+def read_submodules(path: str) -> Iterator[Tuple[bytes, bytes, bytes]]:
+    """read a .gitmodules file."""
+    cfg = ConfigFile.from_path(path)
+    return parse_submodules(cfg)
+
+
 def parse_submodules(config: ConfigFile) -> Iterator[Tuple[bytes, bytes, bytes]]:
     """Parse a gitmodules GitConfig file, returning submodules.
 
diff --git a/dulwich/porcelain.py b/dulwich/porcelain.py
index 0c2d00d26..fd6f2d4aa 100644
--- a/dulwich/porcelain.py
+++ b/dulwich/porcelain.py
@@ -43,6 +43,8 @@
  * remote{_add}
  * receive-pack
  * reset
+ * submodule_add
+ * submodule_init
  * submodule_list
  * rev-list
  * tag{_create,_delete,_list}
@@ -89,6 +91,7 @@
 from dulwich.config import (
     ConfigFile,
     StackedConfig,
+    read_submodules,
 )
 from dulwich.diff_tree import (
     CHANGE_ADD,
@@ -989,6 +992,21 @@ def submodule_add(repo, url, path=None, name=None):
         config.write_to_path()
 
 
+def submodule_init(repo):
+    """Initialize submodules.
+
+    Args:
+      repo: Path to repository
+    """
+    with open_repo_closing(repo) as r:
+        config = r.get_config()
+        gitmodules_path = os.path.join(r.path, '.gitmodules')
+        for path, url, name in read_submodules(gitmodules_path):
+            config.set((b'submodule', name), b'active', True)
+            config.set((b'submodule', name), b'url', url)
+        config.write_to_path()
+
+
 def submodule_list(repo):
     """List submodules.
 
diff --git a/dulwich/tests/test_porcelain.py b/dulwich/tests/test_porcelain.py
index c19cf0ed1..6c38a4ba8 100644
--- a/dulwich/tests/test_porcelain.py
+++ b/dulwich/tests/test_porcelain.py
@@ -1625,6 +1625,10 @@ def test_add(self):
 \tpath = bar
 """, f.read())
 
+    def test_init(self):
+        porcelain.submodule_add(self.repo, "../bar.git", "bar")
+        porcelain.submodule_init(self.repo)
+
 
 class PushTests(PorcelainTestCase):
     def test_simple(self):