Colonel Duncan having admitted that he had written the “Tampico letter,” thus pleading guilty to violating the army regulations, and the President having ordered a court of inquiry and not a court-martial, General Scott declined to prosecute him before this court or a court-martial without express orders from the President.  General Scott considered that it was not for him to attempt to uphold a regulation which the President had revived and then disregarded.  While Colonel Duncan no doubt believed all he had written to be true, the evidence of Colonel H.L.  Scott, assistant adjutant general of the army, Colonel Hitchcock, and Captain Lee shows that the direct attack, or that by Mexicalcingo, was never decided upon.

General Scott was informed that the court of inquiry would probably adjourn to await further orders from the Government.  To prevent this delay, he [Scott] consented to prosecute the case of General Pillow.  With a probability of peace and the disbanding of the army, it was almost certain that there never would be a trial by court-martial should such a court be recommended.

On March 21st the investigation before the court of inquiry commenced in the City of Mexico and continued until April 21st, when the court, as General Scott had predicted, adjourned to the United States for the purpose of obtaining further testimony, and reassembled in Frederick, Md., May 29, 1848.  General Pillow did not appear until June 5th, when General Scott was also present.  The latter had been detained by sickness, and General Pillow had stopped in Tennessee to visit his family.

On July 1st General Scott submitted the following paper to the court, and withdrew the charges against Colonel Duncan: 

“The reason given for withdrawing the first charge was, that the President seemed indisposed to enforce the revised paragraph 650, which he had ordered to be published, and enjoined all to obey and enforce.

“In regard to the second charge and specification, relating to matters of fact set forth in the ‘Tampico letter,’ and which Colonel Duncan had acknowledged over his own signature he had written, General Scott, believing that Colonel Duncan had fallen undesignedly into erroneous statements of fact in the letter, sent an officer to ask him if he was not ignorant, at the time of writing the letter,

“1.  That before the army left Pueblo for the valley his [Scott’s] bias and expectation were that the army would be obliged to reach the enemy’s capital by the left or south around Lakes Chalco and Xochimilco.

“2.  That after his headquarters were established at Ayotla, August 11th, he [Scott] had shown equal solicitude to get additional information of that route, as well as that of Penon or Mexicalcingo.

“3.  That besides sending from Ayotla, August 12th, oral instructions to Brevet Major-General Worth to push further inquiries from Chalco as to the character of the southernmost route around the two lakes, he [Scott] had sent written instructions to General Worth to the same effect from his quarters at Ayotla.[C]