Here is the full list of all 12 Unaided: 1939 achievements.
Kill 10 enemies with a rifle in a single mission.
Kill 5 enemies with a knife in a single mission.
Finish the tutorial.
Kill 5 enemies with a pistol in a single mission.
Kill 5 enemies with a bow in a single mission.
Kill 5 enemies with an explosion in a single mission.
Kill an enemy with a car explosion.
Kill an enemy with a truck explosion.
Kill an enemy with a tank explosion.
Finish a mission without being detected.
Finish a mission with low health.
Finish the story campaign.