According to Le Chatelier's principle, if a system at equilibrium is subjected to a change in temperature, pressure, or concentration, the equilibrium shifts in a direction that counteracts the change.

1. Temperature: The given reaction is exothermic (heat is released as a product). Lowering the temperature removes heat, which favours the forward (exothermic) reaction.
2. Pressure: The forward reaction proceeds with a decrease in the number of gaseous moles ($1 \text{ mol } N_2 + 3 \text{ mol } H_2 = 4 \text{ moles}$ on the reactant side; $2 \text{ moles } NH_3$ on the product side). Increasing the pressure shifts the equilibrium towards the side with fewer gaseous moles to reduce the pressure, which is the forward direction. Therefore, low temperature and high pressure favour the forward reaction.