February 7 is a notable historical day for the acknowledgment of God in modern America: it is the day that a sermon was preached before President Dwight D. Eisenhower, suggesting that the words "under God" be added to the pledge. The sermon was preached by the Rev. George M. Docherty, pastor of New York Avenue Presbyterian Church in Washington, D. C.  (you can download and see the full sermon, with his notes and additions).
This sermon was preached for Lincoln Day, and it had a great impact on those listening, including President Eisenhower, who was seated in the same pew that Abraham Lincoln had regularly occupied in that church as President.  In that sermon Docherty stated:
There was something missing in the pledge, and that which was missing was the characteristics and definitive factor in the American way of life. Indeed apart from the mention of the phrase, the United States of America, it could be the pledge of any republic. In fact, I could hear little Muscovites repeat a similar pledge to their hammer and sickle flag in Moscow with equal solemnity. 
He made the point that the American pledge as it then existed could just have been recited by citizens from any country, even those from communistic nations that hated God. The day following the sermon, U. S. Rep. Charles Oakman from Michigan introduced a Joint Resolution (H. J. Res 371) to add the words "Under God" into the pledge,  explaining:
Mr. Speaker, I think Mr. Docherty hit the nail squarely on the head. One of the most fundamental differences between us and the Communists is our belief in God. 
Two days later, on February 10th, Senator Homer Ferguson from Michigan introduced the Senate Joint Resolution (S.J. 126),  explaining to the Senate:
Our nation is founded on a fundamental belief in God, and the first and most important reason for the existence of our government is to protect the God-given rights of our citizens. . . . Indeed, Mr. President, over one of the doorways to this very Chamber inscribed in the marble are the words “In God We Trust.” Unless those words amount to more than a carving in stone, our country will never be able to defend itself. 
These resolutions were passed, and on June 14, 1954 (Flag Day), President Dwight D. Eisenhower signed the bill into law, officially adding the words "under God" into the Pledge of Allegiance, telling the nation:
From this day forward, the millions of our school children will daily proclaim in every city and town, every village and rural school house, the dedication of our nation and our people to the Almighty. To anyone who truly loves America, nothing could be more inspiring than to contemplate this rededication of our youth, on each school morning, to our country's true meaning. . . . In this way we are reaffirming the transcendence of religious faith in America's heritage and future; in this way we shall constantly strengthen those spiritual weapons which forever will be our country's most powerful resource, in peace or in war. 
Who could have imagined that a single sermon could have such an impact? Yet American history is full of such accounts. On February 7th, take time to read this remarkable sermon, remembering that we are indeed "one nation under God."
George M. Docherty, One Way of Living
(Harper & Brothers, New York, 1958) p. 158, “One Nation Under God.” See also
“History,” New York Avenue Presbyterian Church
Dwight D. Eisenhower: "Statement by the President Upon Signing Bill To Include the Words "Under God" in the Pledge to the Flag," The American Presidency Project,
June 14, 1954 (at: http://www.presidency.ucsb.edu/ws/?pid=9920