The Strawbery Banke Museum in Portsmouth, N.H., is hosting a special Civil War May 1 to Oct. 31 exhibit “Fitz John Porter: Portsmouth’s Civil War Hero or Coward?” as part of its tribute to the 150th anniversary of the Civil War.

Maj. Gen. Fitz John Porter, a native of Portsmouth, had an illustrious career shredded by the political intrigues and a court-martial that ended his military service, said Stephanie Seacord, the museum’s director of communications. He spent the rest of his life trying to repair his reputation.

“Portsmouth men were the first to answer Lincoln’s call for volunteers to fight for the Union cause in the American Civil War,” she said. “More than 3,000 responded, from a city population of 10,000, affecting life at home as well as on the southern battlefields, where they fought.”

The court-martial centered Maj. Gen. John Pope blamed his Porter for the Union lost the Second Battle of Manassas, she said.

During that battle, Pope gave Porter orders that based on Porter’s better knowledge of the enemy’s position, she said. Porter saved his troops from certain disaster, but court martial listened to biased observers with bad maps.

“Even after a military tribunal corrected the account of the incident, it took until 1886 for the pardon that would clear Porter’s name,” she said.

The Museum looks at Porter’s record with an exhibit in the Rowland Gallery that invites visitors to make their own decisions about the verdict, based on the evidence, she said.

The exhibit is based on research in Porter’s letters and the court martial records will include Gen. Fitz John Porter’s sword and his field glasses, she said.

Later in the summer, the City of Portsmouth will host a wreath-laying ceremony at the Gen. Fitz John Porter statue in Haven Park Aug. 6, the 125th anniversary of Porter’s pardon with re-enactors from the New Hampshire 2nd Volunteer Regiment.