At the moment our function only works for one fight. Change it to look like this (note the starting parentheses, and that we've changed "ogre_strength" to "monster_strength"):

def fight(monster_strength):
    global player_strength
    while player_strength > 0 and monster_strength > 0:
        print("You FIGHT!")
        print("SMASH!")
        time.sleep(500)
        print("BASH!")
        time.sleep(500)
        print("Oo!")
        time.sleep(500)
        random_number = random.randint(10)

        if player_strength > random_number:
            print("You won! Gain one strength!")
            player_strength = player_strength + 1
            monster_strength = monster_strength - 1
        else:
            print("You lost! Lose one strength!")
            player_strength = player_strength - 1
            monster_strength = monster_strength + 1
    if player_strength < 1:
        print("Oh no! You died!")
        sys.exit()



Then change the main code to:

    decision = input("You come to a junction. Turn left or right [L,R]: ")

    if decision == "L" or decision == "l":
        print("You turn left and see a terrible ogre!")
        ogre_strength = 2

        fight(ogre_strength)

What we're doing here is passing in ogre_strength so that the function can use it. Inside the function, the number in ogre_strength is copied into monster_strength and the function works with this. But why do this?