8. With the end of the nineteenth and the first decade of the twentieth century, in which occur the first and second Peace Conferences at The Hague and the Naval Conference of London, the development of international law enters upon a new and pregnant epoch. If hitherto, despite the momentous law-making treaties of the nineteenth century, international law was essentially a book-law, a system erected by greater or smaller authorities on the foundations of state practice and in its details often uncertain and contested, it is now subjected more and more, and in a wide domain, to the legislating influence of law-making international conventions. To mention only the principal matters: A code has been issued which, full of lacunae as it is, nevertheless encompasses the whole area of land war; it has been laid down that war shall only be begun by a declaration of war; the employment of force for the recovery of contract-debts has been forbidden; the rights and duties of neutrals in land war and naval war, the treatment of enemy merchant vessels at the outbreak of hostilities, and the conditions of the conversion of merchant vessels into men-of-war have been legislatively fixed; rules concerning the laying of submarine mines, concerning bombardment by naval forces in time of war, concerning the application of the principles of the Geneva Convention to naval warfare, concerning certain limitations on the right of prize in naval warfare have been agreed on; many states have concurred in a prohibition of the discharge of explosive missiles from air-ships; and a code of the rules of naval warfare, so far as it touches the trade of neutrals, dealing with the topics of blockade, contraband of war, unneutral service, destruction of neutral prizes, sale of enemy merchantmen to neutrals, enemy property, convoy and so forth, has been agreed on, though still unratified. [Sidenote: The Permanent Court of Arbitration and other international courts.] 9. It is noteworthy that the first Hague Conference established a permanent international arbitral tribunal and that the second Hague Conference decided on the establishment of an International Prize Court and produced a plan for a standing international court at The Hague. Hitherto there have been no international courts for the decision of disputes, and if contending powers have been ready to refer their disputes to arbitration, they have always first had to form an arbitral tribunal; but now there is in existence an actual International Court of Arbitration, and other international courts are in contemplation. [Sidenote: The Hague Peace Conferences as a permanent institution.]