After the Union army was defeated at the Battle of Bull Run, President Abraham Lincoln declared a National Day of Prayer and Fasting:

It is fit and becoming in all people, at all times, to acknowledge and revere the Supreme Government of God; to bow in humble submission to His chastisement; to confess and deplore their sins and transgressions in the full conviction that the fear of the Lord is the beginning of wisdom; and to pray, with all fervency and contrition, for the pardon of their past offenses, and for a blessing upon their present and prospective action.

And whereas when our own beloved country, once, by the blessings of God, united, prosperous and happy, is now afflicted with faction and civil war, it is peculiarly fit for us to recognize the hand of God in this terrible visitation, and in sorrowful remembrance of our own faults and crimes as a nation and as individuals, to humble ourselves before Him and to pray for His mercy...that the inestimable boon of civil and religious liberty, earned under His guidance and blessing by the labors and sufferings of our fathers, may be restored.

After losing the Second Battle of Bull Run, Lincoln wrote his famous Meditation on the Divine Will:

The will of God prevails. In great contests each party claims to act in accordance with the will of God. Both may be, and one must be wrong. God can not be for and against the same thing at the same time. In the present civil war it is quite possible that God's purpose is something different from the purpose of either party -- and yet the human instrumentalities, working just as they do, are of the best adaptation to effect His purpose.

I am almost ready to say this is probably true -- that God wills this contest, and wills that it shall not end yet. By His mere quiet power, on the minds of the now contestants, He could have either saved or destroyed the Union without a human contest. Yet the contest began. And having begun He could give the final victory to either side any day. Yet the contest proceeds.

President Lincoln is quoted making this statement to Eliza Gurney on October 6, 1862:

If I had my way, this war would never have been commenced. If I had been allowed my way, this war would have ended before this. But we find it still continues; and we must believe that He permits it for some wise purpose of His own, mysterious and unknown to us; and though with our limited understanding we may not be able to comprehend it, yet we cannot but believe, that He who made the world still governs it.

We are indeed going through a great trial -- a fiery trial. In the very responsible position in which I happened to be placed, being a humble instrument in the hands of our Heavenly Father, as I am, and as we all are, to work out His great purposes, I have desired that all my works and acts may be according to His will, and that it might be so, I have sought His aid.

Near the end of 1862, Lincoln made this tremendous statement to Reverend Byron Sunderland:

The ways of God are mysterious and profound beyond all comprehension -- 'Who by searching can find Him out?' God only knows the issue of this business. He has destroyed nations from the map of history for their sins. Nevertheless, my hopes prevail generally above my fears for our Republic. The times are dark, the spirits of ruin are abroad in all their power, and the mercy of God alone can save us.

Here is the text of Lincoln's Proclamation Appointing a National Fast Day, issued March 30, 1863:

Whereas, the Senate of the United States devoutly recognizing the Supreme Authority and just Government of Almighty God in all the affairs of men and of nations, has, by a resolution, requested the President to designate and set apart a day for national prayer and humiliation:

And whereas, it is the duty of nations as well as of men to own their dependence upon the overruling power of God, to confess their sins and transgressions in humble sorrow yet with assured hope that genuine repentance will lead to mercy and pardon, and to recognize the sublime truth, announced in the Holy Scriptures and proven by all history: that those nations only are blessed whose God is Lord:

And, insomuch as we know that, by His divine law, nations like individuals are subjected to punishments and chastisement in this world, may we not justly fear that the awful calamity of civil war, which now desolates the land, may be but a punishment inflicted upon us for our presumptuous sins to the needful end of our national reformation as a whole people?

We have been the recipients of the choicest bounties of Heaven. We have been preserved these many years in peace and prosperity. We have grown in numbers, wealth and power as no other nation has ever grown.

But we have forgotten God. We have forgotten the gracious Hand which preserved us in peace, and multiplied and enriched and strengthened us; and we have vainly imagined, in the deceitfulness of our hearts, that all these blessings were produced by some superior wisdom and virtue of our own.

Intoxicated with unbroken success, we have become too self-sufficient to feel the necessity of redeeming and preserving grace, too proud to pray to the God that made us!

It behooves us then to humble ourselves before the offended Power, to confess our national sins and to pray for clemency and forgiveness.

Now, therefore, in compliance with the request and fully concurring in the view of the Senate, I do, by this proclamation, designate and set apart Thursday, the 30th day of April, 1863, as a day of national humiliation, fasting and prayer.

And I do hereby request all the people to abstain on that day from their ordinary secular pursuits, and to unite, at their several places of public worship and their respective homes, in keeping the day holy to the Lord and devoted to the humble discharge of the religious duties proper to that solemn occasion.

All this being done, in sincerity and truth, let us then rest humbly in the hope authorized by the Divine teachings, that the united cry of the nation will be hard on high and answered with blessing no less than the pardon of our national sins and the restoration of our now divided and suffering country to its former happy condition of unity and peace.

In witness whereof, I have hereunto set my hand and caused the seal of the United States to be affixed. By the President: Abraham Lincoln.

Lincoln remained steadfast in his faith even when General Robert E. Lee led his army of 76,000 men into Pennsylvania. He explained to a general wounded at Gettysburg:

When everyone seemed panic-stricken...I went to my room...and got down on my knees before Almighty God and prayed...Soon a sweet comfort crept into my soul that God Almighty had taken the whole business into His own hands...

On November 19, 1863, Lincoln delivered his famous Gettysburg Address. The entire speech is only 267 words and is engraved on the Lincoln Memorial in Washington, D.C. In it, he talks about America as a nation under God:

Fourscore and seven years ago our fathers brought forth upon this continent a new nation, conceived in liberty, and dedicated to the proposition that all men are created equal. Now we are engaged in a great civil war, testing whether that nation, or any nation so conceived and so dedicated, can long endure.

We are met on a great battlefield of that war. We have come to dedicate a portion of that field as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.

But in a larger sense we cannot dedicate, we cannot consecrate, we cannot hallow this ground. The brave men, living and dead, who struggled here, have consecrated it far above our poor power to add or detract.

The world will little note, nor long remember, what we say here, but it can never forget what they did here. It is for us, the living, rather to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced.

It is rather for us to be here dedicated to the great task remaining before us -- that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion -- that we here highly resolve that these dead shall not have died in vain -- that this nation, under God, shall have a new birth of freedom -- and that government of the people, by the people, for the people, shall not perish from the earth.

During the war, Lincoln overheard someone remark that he hoped "the Lord was on the Union's side." Lincoln responded with this sharp rebuke:

I am not at all concerned about that, for I know that the Lord is always on the side of the right. But it is my constant anxiety and prayer that I and this nation should be on the Lord's side.

On September 5, 1864, the Committee of Colored People from Baltimore presented Lincoln with a Bible. Here's what Lincoln told them in his speech:

In regard to this Great Book, I have but to say, I believe the Bible is the best gift God has given to man. All the good Savior gave to the world was communicated through this Book. But for this Book we could not know right from wrong. All things most desirable for man's welfare, here and hereafter, are to be found portrayed in it. To you I return my most sincere thanks for the elegant copy of the great Book of God which you present.