What happened on 17th April in 1864?

Prisoner Exchanges Were Halted during the US Civil War April 17, 1864

In March 1864, Ulysses Grant assumed command of all Union armies. In April, he ordered a continuation of the established policy of halting prisoner of war exchanges on the basis of the Confederates' mistreatment of African American soldiers of the U.S. army.

Grant stated that the murder of surrendering African American soldiers at Fort Pillow on April 12 motivated him to issue a formal demand that Black and White United States soldiers receive identical consideration in their treatment and exchange as prisoners by the Confederacy.

On April 17, Grant wrote to General Benjamin Butler - who was negotiating a resumption of prisoner exchanges - that "the status of colored prisoners" was a priority. He ordered that Butler should communicate the non-negotiable demand that "no distinction whatever will be made in the exchange between white and colored prisoners," that "the same terms as to treatment while prisoners and conditions of release and exchange must be exacted... in the case of colored soldiers as in the case of white soldiers." "Non-acquiescence by the Confederate authorities," Grant declared, "will be regarded as a refusal on their part to agree to the further exchange of prisoners."

Confederate Secretary of War James Seddon responded with a refusal of the terms. "I doubt," he said, "whether the exchange of negroes at all for our soldiers would be tolerated." Ominously, Seddon added, "As to the white officers serving with negro troops, we ought never to be inconvenienced with such prisoners."

https://www.nps.gov/rich/learn/historyculture/prisoner-exchanges-halted-april-17-1864.htm

The Savannah Breat Riot

https://raycityhistory.wordpress.com/tag/savannah-bread-riot/

The Battle of Plymouth began

https://en.wikipedia.org/wiki/Battle_of_Plymouth_(1864)

A reference for the Savannah bread riot:

http://konreicivilwar.blogspot.com/2014/04/april-17-1864-small-bread-riot.html?m=1

However, food, or "bread", riots had been occurring for several years in the Confederacy.
From https://www.britannica.com/event/American-Civil-War/The-Southern-home-front :

" But the most pressing problem for many civilians in the Confederacy was the threat of starvation. Many causes were at the root of food shortages: a drought in 1862 drove down food supplies; slaves who worked on farms and plantations were fleeing to Union lines; Federal troops were gaining control of more parts of the Confederacy; and, with the Confederate military having priority in terms of transportation, food earmarked for civilians went bad before it could be shipped from warehouses. When the government tried to rectify the situation by impressing food, farmers responded by hiding their crops and their livestock. Hyperinflation sent the price of food skyrocketing while the value of the Confederate dollar cratered. Food riots broke out in several cities, including Richmond. In that instance, in April 1863, Davis ordered the militia to open fire on several hundred women if they did not leave the area, which they grudgingly did."

Wikipedia focuses on the riot in Richmond, the capitol of the Confederacy, the previous year.

https://en.m.wikipedia.org/wiki/Southern_bread_riots