His duties, through 1917, included teaching at the United States Military Academy and authoring, with John Henry Wigmore, the dean of Northwestern University's law school, the Army's first rules of evidence for courts-martial.

As governor, Winship's primary mission was to crush the Puerto Rican Nationalist Party, by imprisoning its leadership and intimidating the rank-and-file membership.

[4] Upon arrival he immediately set out to "militarize" the Insular Police force, arming it with machine guns and riot control equipment.

Winship also recruited a new police chief, E. Francis Riggs, whose background was in military intelligence, and whose immediate prior occupation had been to "advise" Anastasio Somoza in Nicaragua.

The party's president, Pedro Albizu Campos, and others were sentenced to 10 years in prison by a United States federal court.

On Palm Sunday (March 21), 1937, Governor Winship cancelled a Nationalist parade, which was to have taken place in Ponce to commemorate the 1873 abolition of slavery, only an hour before it was to have begun.

Congressman Vito Marcantonio of New York also criticized Winship, and in 1939, President Roosevelt eventually replaced him as governor of Puerto Rico.

[10] A second panel, an independent investigation led by Arthur Garfield Hays, general counsel of the American Civil Liberties Union, with Fulgencio Pinero, Emilio Belaval, Jose Davila Rice, Antonio Ayuso Valdivieso, Manuel Diaz Garcia, and Franscisco M. Zeno, as members, concluded that the police acted as a mob, and that the events on March 21 constituted a massacre.

[12] Almost simultaneously with the prosecutor's investigation, a federal law which allowed public officials to be indicted was repealed, effectively granting Governor Winship immunity from further prosecution.

The following year, Governor Winship moved the celebration of the 40th anniversary of the United States invasion of Puerto Rico from the traditional San Juan location to the city of Ponce.

During this time, he served as one of the presiding judges of a military tribunal in the United States during the trial of eight German saboteurs who were arrested in the country.

Men, women, and children were massacred in the streets of the island simply because they dared to express their opinion or attempted to meet in free assemblage."