In the US presidential election of 1916, Paul and the NWP campaigned in western states where women could already vote against the continuing refusal of President Woodrow Wilson and other incumbent Democrats to actively support the Suffrage Amendment. In January 1917, the NWP staged the first political protest and picketing at the White House. The pickets, participating in a nonviolent civil disobedience campaign known as the "Silent Sentinels," held banners demanding the right to vote.  After the United States entered World War I in April 1917, many people viewed the picketing Silent Sentinels as disloyal. In June 1917, picketers were arrested on charges of "obstructing traffic." Over the next six months, many, including Alice, were convicted and incarcerated at the Occoquan Workhouse in Virginia (which later became the Lorton Correctional Complex) and the District of Columbia Jail.  When the public heard the news of the first arrests some were surprised that leading suffragists and very well-connected women were going to prison for peacefully protesting. President Wilson received bad publicity from this event, and was livid with the position he was forced into. He quickly pardoned the first women arrested on July 19, two days after they had been sentenced, but reporting on the arrests and abuses continued. The Boston Journal, for example, stated, "The little band representing the NWP has been abused and bruised by government clerks, soldiers and sailors until its efforts to attract the President's attention has sunk into the conscience of the whole nation."  Suffragists continued picketing outside the White House after the Wilson pardon, and throughout World War I. Their banners contained such slogans as "Mr. President, How Long Must Women Wait For Liberty?". Although the suffragists protested peacefully, their protests were sometimes violently opposed. While protesting, young men would harass and beat the women, with the police never intervening on behalf of the protesters. Police would even arrest other men who tried to help the women who were getting beaten. Even though they were protesting during wartime, they maintained public support by agitating peacefully. Throughout this time, more protesters were arrested and sent to Occoquan or the District Jail. Pardons were no longer offered.

Answer this question "what are silent sentenials?" by extracting the answer from the text above.
The pickets, participating in a nonviolent civil disobedience campaign known as the "Silent Sentinels," held banners demanding the right to vote.