Here are some more detailed examples, taken from "Baha'u'llah and a New Era," which is a really good introductory book to the Faith.
Napoleon III
In the year 1869 Baha'u'llah wrote to Napoleon III, rebuking him for his lust of war and for the contempt with which he had treated a former letter from Baha'u'llah. The Epistle contains the following stern warning: --
For what thou hast done, thy kingdom shall be thrown into confusion, and thine empire shall pass from thine hands, as a punishment for that which thou hast wrought. Then wilt thou know how thou hast plainly erred. Commotions shall seize all the people in that land, unless thou arisest to held this Cause, and followest Him Who is the Spirit of God (Jesus Christ) in this, the Straight Path. Hath thy pomp made thee proud? By My Life! It shall not endure; nay, it shall soon pass away, unless thou holdest fast by this firm Cord. We see abasement hastening after thee, whilst thou art of the heedless.
Needless to say, Napoleon, who was then at the zenith of his power, paid no heed to this warning. In the following year he went to war with Prussia, firmly convinced that his troops could easily gain Berlin; but the tragedy foretold by Baha'u'llah overwhelmed him. He was defeated at Saarbruck, at Weisenburg, at Metz, and finally in the crushing catastrophe at Sedan. He was then carried prisoner to Prussia, and came to a miserable end in England two years later.
Germany
Baha'u'llah later gave an equally solemn warning to the conquerors of Napoleon, which also fell on deaf ears and received a terrible fulfillment. In the Book of Aqdas, which was begun in Adrianople, and finished in the early years of Baha'u'llah's imprisonment in Akka, He addressed the Emperor of Germany as follows: --
O King of Berlin! ... Do thou remember the one whose power transcended thy power (Napoleon III) and whose station excelled thy station. Where is he? Whither are gone the things he possessed? Take warning, and be not of them that are fast asleep. He it was who cast the Tablet of God behind him, when We made known unto him what the hosts of tyranny had caused Us to suffer. Wherefore, disgrace assailed him from all sides, and he went down to dust in great loss. Think deeply, O King, concerning him, and concerning them who, like unto thee, have conquered cities and ruled over men. The All-Merciful brought them down from their palaces to their graves. Be warned, be of them who reflect.
...
O banks of the Rhine! We have seen you covered with gore, inasmuch as the swords of retribution were drawn against you; and you shall have another turn. And We hear the lamentations of Berlin, though she be today in conspicuous glory. -- Kitab-i-Aqdas.
During the period of German successes in the Great War of 1914-1918, and especially during the last great German offensive in the spring of 1918, this well-known prophecy was extensively quoted by the opponents of the Bahá'í Faith in Persia, in order to discredit Baha'u'llah; but when the forward sweep of the victorious Germans was suddenly transformed into crushing, overwhelming disaster, the efforts of these enemies of the Bahá'í Cause recoiled on themselves, and the notoriety which they had given to the prophecy became a powerful means of enhancing the reputation of Baha'u'llah.
Persia
In the Book of Aqdas written when the tyrannical Nasiri'd-Din Shah was at the height of his power, Baha'u'llah blesses the city of Tihran, which is the capital of Persia, and His own birthplace, and says of it: --
Let nothing grieve thee, O Land of Ta (Tihran), for God hath chosen thee to be the source of the joy of all mankind. He shall, if it be His will, bless thy throne with one who will rule with justice, who will gather together the flock of God which the wolves have scattered. Such a ruler will, with joy and gladness, turn his face towards, and extend his favors unto, the people of Baha. He indeed is accounted in the sight of God as a jewel among men. Upon him rest forever the glory of God, and the glory of all that dwell in the kingdom of His Revelation.
Rejoice with great joy, for God hath made thee "the Day Spring of His light," inasmuch as within thee was born the Manifestation of His Glory. Be thou glad for this name that hath been conferred upon thee -- a name through which the Day Star of Grace hath shed its splendor, through which both earth and heaven have been illumined.
Ere long will the state of affairs within thee be changed, and the reins of power fall into the hands of the people. Verily, thy Lord is the All-Knowing. His authority embraceth all things. Rest thou assured in the gracious favor of thy Lord. The eye of His loving-kindness shall everlastingly be directed towards thee. The day is approaching when thy agitation will have been transmuted into peace and quiet calm. Thus hath it been decreed in the wondrous Book. -- Gleanings from the Writings of Baha'u'llah, pp. 110-111.
So far, Persia has only begun to emerge from the period of confusion foretold by Baha'u'llah, but already constitutional government has been started, and signs are not lacking that a brighter era is at hand.
Turkey
To the Sultan of Turkey and his Prime Minister `Ali Pasha, Baha'u'llah, then (in 1868) confined in a Turkish prison, addressed some of His most solemn, grave warnings. To the Sultan He wrote from the Barracks at Akka: --
O thou who considerest thyself the greatest of all men ... erelong thy name shall be forgotten and thou shalt find thyself in great loss. According to thy opinion, this Quickener of the world and its Peacemaker is culpable and seditious. What crime have the women, children and suffering babes committed to merit thy wrath, oppression and hate? You have persecuted a number of souls who have shown no opposition in your country, and who have instigated no revolution against the government; nay, rather, by day and by night they have been peacefully engaged in the mentioning of God. You have pillaged their properties, and through your tyrannical acts, all that they had was taken from them. ... Before God, a handful of dust is greater than your kingdom, glory, sovereignty and dominion, and should He desire, He would scatter you as the sand of the desert. Erelong His wrath shall overtake you, revolutions shall appear in your midst and your countries will be divided! Then you will weep and lament and nowhere will you find help and protection. ... Be ye watchful, for the wrath of God is prepared, and erelong you shall behold that which is written by the Pen of Command.
And to Ali Pasha He wrote: --
Thou hast, O Chief, committed that which hath made Muhammad, the Apostle of God, groan in the Most Exalted Paradise. The world hath made thee proud, so much so that thou hast turned away from the Face through Whose brightness the Concourse on high hath been illumined. Soon thou shalt find thyself in evident loss. Thou didst unite with the Ruler of Persia for doing Me harm, although I had come to you from the Dawning-place of the Almighty, the Great, with a Cause which refreshed the eyes of the favored ones of God. ...
Didst thou think that thou could put out the fire which God hath enkindled in the Universe? No! I declare by His True Soul, wert thou of those who understand. More than that, by what thou hast done its blaze and flame have been increased. Soon it will encompass the world and its inhabitants. ... The day is approaching when the Land of Mystery (Adrianople) and what is beside it shall be changed, and shall pass out of the hands of the King, and commotions shall appear, and the voice of lamentation shall be raised, and the evidences of mischief shall be revealed on all sides, and confusion shall spread by reason of that which hath befallen these captives [Baha'u'llah and His companions] at the hands of the hosts of oppression. The course of things shall be altered, and conditions shall wax so grievous, that the very sand on the desolate hills will moan, and the trees on the mountain will weep, and blood will flow out of all things. Then wilt thou behold the people in sore distress. ...
Thus hath the matter been decreed on the part of the Designer, the Wise, Whose command the hosts of heaven and earth could not withstand, nor could all the kings and rulers withhold Him from that which He willeth. Calamities are the oil for this Lamp, and through them its Light increaseth, were ye of those who know! All oppositions displayed by the oppressors are indeed as heralds to this Faith, and by them the appearance of God and His Cause have become widely spread among the people of the world.
Again in the Book of Aqdas He wrote: --
O Spot [Constantinople] that art situate on the shores of the two seas! The throne of tyranny hath, verily, been established upon thee, and the flame of hatred hath been kindled within thy bosom, in such wise that the Concourse on high and they who circle around the Exalted Throne have wailed and lamented. We behold in thee the foolish ruling over the wise, and darkness vaunting itself against the light. Thou art indeed filled with manifest pride. Hath thine outward splendor made thee vainglorious? By Him Who is the Lord of mankind! It shall soon perish, and thy daughters and thy widows and all the kindreds that dwell within thee shall lament. Thus informeth thee the All-Knowing, the All-Wise.
The successive calamities which have befallen this once great empire since the publication of these warnings have furnished an eloquent commentary on their prophetic significance.
America
In the Book of Aqdas, revealed in Akka in 1873, Baha'u'llah appealed to America as follows: --
O Rulers of America and the Presidents of the Republics therein ... Give ear unto that which hath been raised from the Dayspring of Grandeur: Verily, there is none other God but Me, the Lord of Utterance, the All-Knowing. Bind ye the broken with the hands of justice, and crush the oppressor who flourisheth with the rod of the commandments of your Lord, the Ordainer, the All-Wise. -- Kitab-i-Aqdas.
Abdu'l-Baha in His addresses in America and elsewhere frequently expressed the hope, the prayer and the assurance that the banner of international peace would be first raised in America. At Cincinnati, Ohio, on November 5, 1912, He said: --
America is a noble nation, a standard-bearer of peace throughout the world, shedding her light to all regions. Other nations are not untrammeled and free of intrigues like the United States, and are unable to bring about Universal Peace. But America, thank God, is at peace with all the world, and is worthy of raising the flag of brotherhood and International Peace. When the summons to International Peace is raised by America, all the rest of the world will cry: "Yes, we accept." The nations of every clime will join in adopting the teachings of Baha'u'llah, revealed over fifty years ago. In His Epistles He asked the parliaments of the world to send their best and wisest men to an international world parliament that should decide all questions between the peoples and establish peace ... then we shall have the Parliament of Man of which the prophets have dreamed.
The appeals of Baha'u'llah and Abdu'l-Baha have already been responded to, in a large measure, by the United States of America, and in no country of the world have the Bahá'í teachings met with readier acceptance. The role assigned to America, of summoning the nations to international peace, has as yet, however, been only partially played, and Bahá'ís are awaiting with interest the developments which the future has in store.1
The Great War
Both Baha'u'llah and Abdu'l-Baha on many occasions foretold with surprising accuracy the coming of the Great War of 1914-1918. At Sacramento, California, on October 26, 1912, Abdu'l-Baha said: -- "Today the European continent is like an arsenal. It is a storehouse of explosives, ready for just a spark, and one spark could set aflame the whole of Europe, particularly at this time, when the Balkan question is before the world."
In many of His addresses in America and Europe He gave similar warning. In another address in California in October 1912 He said: --
We are on the eve of the Battle of Armageddon referred to in the sixteenth chapter of Revelation. The time is two years hence, when only a spark will set aflame the whole of Europe.
The social unrest in all countries, the growing religious scepticism antecedent to the millennium, and already here, will set aflame the whole of Europe as is prophesied in the Book of Daniel and in the Book (Revelation) of John.
By 1917 kingdoms will fall and cataclysms will rock the earth. (Reported by Mrs. Corinne True in The North Shore Review, September 26, 1914, Chicago, U.S.A.)
On the eve of the great conflict He said: --
A great melee of the civilized nations is in sight. A tremendous conflict is at hand. The world is at the threshold of a most tragic struggle. ... Vast armies -- millions of men -- are being mobilized and stationed at their frontiers. They are being prepared for the fearful contest. The slightest friction will bring them into a terrific crash, and there will be a conflagration, the like of which is not recorded in the past history of mankind. (At Haifa, August 3, 1914).
