Neutrality is the status assigned to non‐belligerent states in time of war. Since classical times (500
BCE
to 600
CE
), neutrality has featured in the international system. It is a contested and complex subject affected by a range of essential state concerns including: maritime affairs relating to shipping, trade, and the open seas; the conduct of warfare on sea, land, and in the air; the limits of territorial sovereignty; impartiality; and the conduct of states and their subjects in time of war. Over time, neutrality's applicability altered with changes in the international system and in response to the needs of governments. In the early modern period (1400–1800
CE
), neutrality featured as an important field in international law, but it was not until the turn of the nineteenth century, at the two Hague conferences of 1899 and 1907, that neutrality became formally codified. Through the twentieth and twenty‐first centuries neutrality accommodated contradictory definitions in international relations.