U.S. Secretary of State John Kerry will deliver the keynote address at the Vietnam War Summit this month at the LBJ Presidential Library, a gathering that will spotlight a critical, difficult point in Lyndon B. Johnson’s administration.

Kerry, who served in the Navy during the war, will speak April 27, in the middle of the three-day event, before accompanying President Obama on his first Vietnam visit in May. The secretary of state is expected to focus on the changes in Vietnam and in its relationship with the United States.

The summit is hosted by the University of Texas at Austin and the library, whose officials promised an unflinching look at the war.