To overcome Johnson's vetoes required two-thirds of each House of Congress; to impeach and remove him would require only a majority of the House and two-thirds of the Senate.
The desired occasion for impeachment was furnished by Johnson's attempt to get Edwin M.Stanton, the Secretary of War, out of the Cabinet.
Stanton held radical views and was at no time sympathetic with or loyal to Johnson, but he loved office too well to resign along with those cabinet members who could not follow the President in his struggle with Congress.

He was seldom frank and sincere in his dealings with the President, and kept up an underhand correspondence with the radical leaders, even assisting in framing some of the reconstruction legislation which was designed to render Johnson powerless.

In him the radicals had a representative within the President's Cabinet.
Wearied of Stanton's disloyalty, Johnson asked him to resign and, upon a refusal, suspended him in August 1867, and placed General Grant in temporary charge of the War Department.

General Grant, Chief Justice Chase, and Secretary McCulloch, though they all disliked Stanton, advised the President against suspending him.

But Johnson was determined.