diff --git a/src/client/embedded/alpha/client_proto_context.ml b/src/client/embedded/alpha/client_proto_context.ml
index 3be8bf7e7..2dfeb0c56 100644
--- a/src/client/embedded/alpha/client_proto_context.ml
+++ b/src/client/embedded/alpha/client_proto_context.ml
@@ -148,6 +148,19 @@ let faucet cctxt block ?force ~manager_pkh () =
     ~net ~id:manager_pkh () >>=? fun bytes ->
   originate cctxt ?force ~block bytes
 
+let dictate cctxt block command seckey =
+  Client_node_rpcs.Blocks.net cctxt block >>= fun net ->
+  Client_proto_rpcs.Helpers.Forge.Dictator.operation
+    cctxt block ~net command >>=? fun bytes ->
+  let signature = Ed25519.sign seckey bytes in
+  let signed_bytes = MBytes.concat bytes signature in
+  let oph = Operation_hash.hash_bytes [ signed_bytes ] in
+  Client_node_rpcs.inject_operation cctxt ~wait:true signed_bytes >>=? fun injected_oph ->
+  assert (Operation_hash.equal oph injected_oph) ;
+  cctxt.message "Operation successfully injected in the node." >>= fun () ->
+  cctxt.message "Operation hash is '%a'." Operation_hash.pp oph >>= fun () ->
+  return ()
+
 let group =
   { Cli_entries.name = "context" ;
     title = "Block contextual commands (see option -block)" }
@@ -275,5 +288,33 @@ let commands () =
             (fun c -> cctxt.message "New contract %a originated from a smart contract."
                 Contract.pp c)
             contracts >>= fun () -> return ()) >>=
-         Client_proto_rpcs.handle_error cctxt)
+         Client_proto_rpcs.handle_error cctxt) ;
+    command ~desc: "Activate a protocol" begin
+      prefixes [ "activate" ; "protocol" ] @@
+      param ~name:"version" ~desc:"Protocol version (b58check)"
+        (fun _ p -> Lwt.return @@ Protocol_hash.of_b58check p) @@
+      prefixes [ "with" ; "key" ] @@
+      param ~name:"password" ~desc:"Dictator's key"
+        (fun _ key ->
+           Lwt.return (Environment.Ed25519.Secret_key.of_b58check key))
+        stop
+    end
+      (fun hash seckey cctxt ->
+         let block = Client_config.block () in
+         dictate cctxt block (Activate hash) seckey >>=
+         Client_proto_rpcs.handle_error cctxt) ;
+    command ~desc: "Fork a test protocol" begin
+      prefixes [ "fork" ; "test" ; "protocol" ] @@
+      param ~name:"version" ~desc:"Protocol version (b58check)"
+        (fun _ p -> Lwt.return (Protocol_hash.of_b58check p)) @@
+      prefixes [ "with" ; "key" ] @@
+      param ~name:"password" ~desc:"Dictator's key"
+        (fun _ key ->
+           Lwt.return (Environment.Ed25519.Secret_key.of_b58check key))
+        stop
+    end
+      (fun hash seckey cctxt ->
+         let block = Client_config.block () in
+         dictate cctxt block (Activate_testnet hash) seckey >>=
+         Client_proto_rpcs.handle_error cctxt) ;
   ]
diff --git a/src/client/embedded/alpha/client_proto_rpcs.ml b/src/client/embedded/alpha/client_proto_rpcs.ml
index 8ac00eccc..fb052ecf7 100644
--- a/src/client/embedded/alpha/client_proto_rpcs.ml
+++ b/src/client/embedded/alpha/client_proto_rpcs.ml
@@ -236,6 +236,19 @@ module Helpers = struct
         operations cctxt b ~net ~source
           Tezos_context.[Endorsement { block ; slot }]
     end
+    module Dictator = struct
+      let operation cctxt
+          block ~net operation =
+        let op = Dictator_operation operation in
+        (call_error_service1 cctxt Services.Helpers.Forge.operations block
+           ({net_id=net}, Sourced_operations op))
+      let activate cctxt
+          b ~net hash =
+          operation cctxt b ~net (Activate hash)
+      let activate_testnet cctxt
+          b ~net hash =
+          operation cctxt b ~net (Activate_testnet hash)
+    end
     module Anonymous = struct
       let operations cctxt block ~net operations =
         (call_error_service1 cctxt Services.Helpers.Forge.operations block
diff --git a/src/client/embedded/alpha/client_proto_rpcs.mli b/src/client/embedded/alpha/client_proto_rpcs.mli
index c4cc20ba2..da4866c57 100644
--- a/src/client/embedded/alpha/client_proto_rpcs.mli
+++ b/src/client/embedded/alpha/client_proto_rpcs.mli
@@ -238,6 +238,26 @@ module Helpers : sig
         public_key_hash option ->
         MBytes.t tzresult Lwt.t
     end
+    module Dictator : sig
+      val operation:
+        Client_commands.context ->
+        block ->
+        net:Updater.Net_id.t ->
+        dictator_operation ->
+        MBytes.t tzresult Lwt.t
+      val activate:
+        Client_commands.context ->
+        block ->
+        net:Updater.Net_id.t ->
+        Protocol_hash.t ->
+        MBytes.t tzresult Lwt.t
+      val activate_testnet:
+        Client_commands.context ->
+        block ->
+        net:Updater.Net_id.t ->
+        Protocol_hash.t ->
+        MBytes.t tzresult Lwt.t
+    end
     module Delegate : sig
       val operations:
         Client_commands.context ->
diff --git a/src/proto/alpha/TEZOS_PROTOCOL b/src/proto/alpha/TEZOS_PROTOCOL
index 787ccb742..b011da7eb 100644
--- a/src/proto/alpha/TEZOS_PROTOCOL
+++ b/src/proto/alpha/TEZOS_PROTOCOL
@@ -1,7 +1,6 @@
 {
     "hash": "ProtoALphaALphaALphaALphaALphaALphaALphaALphaDdp3zK",
     "modules": [
-
         "Misc",
         "Tezos_hash",
 
diff --git a/src/proto/alpha/apply.ml b/src/proto/alpha/apply.ml
index c761d2ffa..85efbbc80 100644
--- a/src/proto/alpha/apply.ml
+++ b/src/proto/alpha/apply.ml
@@ -153,6 +153,17 @@ let apply_sourced_operation
             ctxt delegate pred_block block_prio content)
         ctxt contents >>=? fun ctxt ->
       return (ctxt, origination_nonce)
+  | Dictator_operation (Activate hash) ->
+      let dictator_pubkey = Constants.dictator_pubkey ctxt in
+      Operation.check_signature dictator_pubkey operation >>=? fun () ->
+      activate ctxt hash >>= fun ctxt ->
+      return (ctxt, origination_nonce)
+  | Dictator_operation (Activate_testnet hash) ->
+      let dictator_pubkey = Constants.dictator_pubkey ctxt in
+      Operation.check_signature dictator_pubkey operation >>=? fun () ->
+      set_test_protocol ctxt hash >>= fun ctxt ->
+      fork_test_network ctxt >>= fun ctxt ->
+      return (ctxt, origination_nonce)
 
 let apply_anonymous_operation ctxt miner_contract origination_nonce kind =
   match kind with
@@ -282,9 +293,12 @@ let compare_operations op1 op2 =
   | Sourced_operations _, Anonymous_operations _ -> 1
   | Sourced_operations op1, Sourced_operations op2 ->
       match op1, op2 with
-      | Delegate_operations _, Manager_operations _ -> -1
-      | Manager_operations _, Delegate_operations _ -> 1
+      | Delegate_operations _, (Manager_operations _ | Dictator_operation _) -> -1
+      | Manager_operations _, Dictator_operation _ -> -1
+      | Dictator_operation _, Manager_operations _ -> 1
+      | (Manager_operations _ | Dictator_operation _), Delegate_operations _ -> 1
       | Delegate_operations _, Delegate_operations _ -> 0
+      | Dictator_operation _, Dictator_operation _ -> 0
       | Manager_operations op1, Manager_operations op2 -> begin
           (* Manager operations with smaller counter are pre-validated first. *)
           Int32.compare op1.counter op2.counter
diff --git a/src/proto/alpha/constants_repr.ml b/src/proto/alpha/constants_repr.ml
index 65f84449e..3c94e977a 100644
--- a/src/proto/alpha/constants_repr.ml
+++ b/src/proto/alpha/constants_repr.ml
@@ -43,6 +43,7 @@ type constants = {
   instructions_per_transaction: int ;
   proof_of_work_threshold: int64 ;
   bootstrap_keys: Ed25519.Public_key.t list ;
+  dictator_pubkey: Ed25519.Public_key.t ;
 }
 
 let read_public_key s =
@@ -69,7 +70,10 @@ let default = {
       "9c328bddf6249bbe550121076194d99bbe60e5b1e144da4f426561b5d3bbc6ab" ;
       "a3db517734e07ace089ad0a2388e7276fb9b114bd79259dd5c93b0c33d57d6a2" ;
       "6d2d52e62f1d48f3cf9badbc90cfe5f3aa600194bf21eda44b8e64698a82d341" ;
-    ]
+    ] ;
+  dictator_pubkey =
+    read_public_key
+      "4d5373455738070434f214826d301a1c206780d7f789fcbf94c2149b2e0718cc";
 }
 
 let opt (=) def v = if def = v then None else Some v
@@ -113,6 +117,9 @@ let constants_encoding =
        and bootstrap_keys =
          opt Compare_keys.(=)
            default.bootstrap_keys c.bootstrap_keys
+       and dictator_pubkey =
+         opt Ed25519.Public_key.(=)
+           default.dictator_pubkey c.dictator_pubkey
        in
        (( cycle_length,
           voting_period_length,
@@ -122,7 +129,8 @@ let constants_encoding =
           max_signing_slot,
           instructions_per_transaction,
           proof_of_work_threshold,
-          bootstrap_keys), ()) )
+          bootstrap_keys,
+          dictator_pubkey), ()) )
     (fun (( cycle_length,
             voting_period_length,
             time_before_reward,
@@ -131,7 +139,8 @@ let constants_encoding =
             max_signing_slot,
             instructions_per_transaction,
             proof_of_work_threshold,
-            bootstrap_keys), ()) ->
+            bootstrap_keys,
+            dictator_pubkey), ()) ->
       { cycle_length =
           unopt default.cycle_length cycle_length ;
         voting_period_length =
@@ -152,10 +161,12 @@ let constants_encoding =
           unopt default.proof_of_work_threshold proof_of_work_threshold ;
         bootstrap_keys =
           unopt default.bootstrap_keys bootstrap_keys ;
+        dictator_pubkey =
+          unopt default.dictator_pubkey dictator_pubkey ;
       } )
      Data_encoding.(
        merge_objs
-         (obj9
+         (obj10
             (opt "cycle_length" int32)
             (opt "voting_period_length" int32)
             (opt "time_before_reward" int64)
@@ -164,7 +175,8 @@ let constants_encoding =
             (opt "max_signing_slot" int31)
             (opt "instructions_per_transaction" int31)
             (opt "proof_of_work_threshold" int64)
-            (opt "bootstrap_keys" (list Ed25519.Public_key.encoding)))
+            (opt "bootstrap_keys" (list Ed25519.Public_key.encoding))
+            (opt "dictator_pubkey" Ed25519.Public_key.encoding))
          unit)
 
 type error += Constant_read of exn
diff --git a/src/proto/alpha/operation_repr.ml b/src/proto/alpha/operation_repr.ml
index 249616e95..20c32b9d0 100644
--- a/src/proto/alpha/operation_repr.ml
+++ b/src/proto/alpha/operation_repr.ml
@@ -42,6 +42,7 @@ and sourced_operations =
       source: Ed25519.Public_key.t ;
       operations: delegate_operation list ;
     }
+  | Dictator_operation of dictator_operation
 
 and manager_operation =
   | Transaction of {
@@ -78,6 +79,10 @@ and delegate_operation =
       ballot: Vote_repr.ballot ;
     }
 
+and dictator_operation =
+  | Activate of Protocol_hash.t
+  | Activate_testnet of Protocol_hash.t
+
 and counter = Int32.t
 
 module Encoding = struct
@@ -236,11 +241,40 @@ module Encoding = struct
         | _ -> None)
       (fun (source, operations) -> Delegate_operations { source ; operations })
 
+  let dictator_kind_encoding =
+    let mk_case name args =
+      let open Data_encoding in
+      conv
+        (fun o -> ((), o))
+        (fun ((), o) -> o)
+        (merge_objs
+           (obj1 (req "network" (constant name)))
+           args) in
+    let open Data_encoding in
+    union ~tag_size:`Uint8 [
+      case ~tag:0
+        (mk_case "activate"
+           (obj1 (req "hash" Protocol_hash.encoding)))
+        (function (Activate hash) -> Some hash | _ -> None)
+        (fun hash -> Activate hash) ;
+      case ~tag:1
+        (mk_case "activate_testnet"
+           (obj1 (req "hash" Protocol_hash.encoding)))
+        (function (Activate_testnet hash) -> Some hash | _ -> None)
+        (fun hash -> Activate_testnet hash) ;
+    ]
+
+  let dictator_kind_case tag =
+    case ~tag dictator_kind_encoding
+      (function Dictator_operation op -> Some op | _ -> None)
+      (fun op -> Dictator_operation op)
+
   let signed_operations_case tag =
     case ~tag
       (union [
           manager_kind_case 0 ;
           delegate_kind_case 1 ;
+          dictator_kind_case 2 ;
         ])
       (function Sourced_operations ops -> Some ops | _ -> None)
       (fun ops -> Sourced_operations ops)
diff --git a/src/proto/alpha/operation_repr.mli b/src/proto/alpha/operation_repr.mli
index d935daaec..99c425944 100644
--- a/src/proto/alpha/operation_repr.mli
+++ b/src/proto/alpha/operation_repr.mli
@@ -42,6 +42,7 @@ and sourced_operations =
       source: Ed25519.Public_key.t ;
       operations: delegate_operation list ;
     }
+  | Dictator_operation of dictator_operation
 
 and manager_operation =
   | Transaction of {
@@ -78,6 +79,10 @@ and delegate_operation =
       ballot: Vote_repr.ballot ;
     }
 
+and dictator_operation =
+  | Activate of Protocol_hash.t
+  | Activate_testnet of Protocol_hash.t
+
 and counter = Int32.t
 
 type error += Cannot_parse_operation
diff --git a/src/proto/alpha/services_registration.ml b/src/proto/alpha/services_registration.ml
index 027ff0b12..0072be745 100644
--- a/src/proto/alpha/services_registration.ml
+++ b/src/proto/alpha/services_registration.ml
@@ -466,6 +466,10 @@ let check_signature ctxt signature shell contents =
   | Sourced_operations (Delegate_operations { source }) ->
       Operation.check_signature source
         { signature ; shell ; contents ; hash = dummy_hash }
+  | Sourced_operations (Dictator_operation _) ->
+     let key = Constants.dictator_pubkey ctxt in
+     Operation.check_signature key
+       { signature ; shell ; contents ; hash = dummy_hash }
 
 let parse_operations ctxt (shell, bytes, check) =
   Operation.parse_proto bytes >>=? fun (proto, signature) ->
diff --git a/src/proto/alpha/tezos_context.ml b/src/proto/alpha/tezos_context.ml
index 99a5fc254..a4a92deb2 100644
--- a/src/proto/alpha/tezos_context.ml
+++ b/src/proto/alpha/tezos_context.ml
@@ -70,6 +70,9 @@ module Constants = struct
   let proof_of_work_threshold c =
     let constants = Storage.constants c in
     constants.proof_of_work_threshold
+  let dictator_pubkey c =
+    let constants = Storage.constants c in
+    constants.dictator_pubkey
 end
 
 module Public_key = struct
diff --git a/src/proto/alpha/tezos_context.mli b/src/proto/alpha/tezos_context.mli
index 1c9d820d9..4f1ced13b 100644
--- a/src/proto/alpha/tezos_context.mli
+++ b/src/proto/alpha/tezos_context.mli
@@ -183,6 +183,7 @@ module Constants : sig
   val max_signing_slot: context -> int
   val instructions_per_transaction: context -> int
   val proof_of_work_threshold: context -> int64
+  val dictator_pubkey: context -> Ed25519.Public_key.t
 
 end
 
@@ -459,6 +460,7 @@ and sourced_operations =
       source: public_key ;
       operations: delegate_operation list ;
     }
+  | Dictator_operation of dictator_operation
 
 and manager_operation =
   | Transaction of {
@@ -495,6 +497,10 @@ and delegate_operation =
       ballot: Vote.ballot ;
     }
 
+and dictator_operation =
+  | Activate of Protocol_hash.t
+  | Activate_testnet of Protocol_hash.t
+
 and counter = Int32.t
 
 module Operation : sig