The instrument ‘Abdu’l-Baha devised for the proclamation of the Faith to the remotest corners of the Earth was the Divine Plan laid out in the fourteen great Tablets of the Divine Plan

As war's inferno was engulfing the world, 'Abdu'l-Bahá turned His attention to the one great task remaining in His ministry, that of ensuring the proclamation to the remotest corners of the Earth of the message which had been neglected -- or opposed -- in Islamic and Western society alike. The instrument He devised for this purpose was the Divine Plan laid out in fourteen great Tablets, four of them addressed to the Bahá'í community of North America and ten subsidiary ones addressed to five specific segments of that community. Together with Bahá'u'lláh's Tablet of Carmel and the Master's Will and Testament, the Tablets of the Divine Plan were described by Shoghi Effendi as three of the "Charters" of the Cause. Revealed during the darkest days of the war, in 1916 and 1917, the Divine Plan summoned the small body of American and Canadian believers to assume the role of leadership in establishing the Cause of God throughout the planet. The implications of the trust were awe-inspiring. 
(‘Century of Light’ document, prepared under the supervision of the Universal House of Justice and published in 2001)