 Its spread across the country is commonly attributed to its use in the Japanese Army and Navy which adopted it extensively as convenient field and naval canteen cooking, allowing even conscripts from the remotest countryside to experience the dish.The Japan Maritime Self-Defense Force traditionally have curry every Friday for lunch and many ships have their own unique recipes.The standard Japanese curry contains onions, carrots, potatoes, and sometimes celery, and a meat that is cooked in a large pot.