Navy Adm. Samuel Locklear, now retired, speaks at the Pentagon in 2014.
The retired top brass signed the letter backing Biden along with nearly 300 other former national security officials and diplomats.
Abbot served as commander of the U.S. Sixth Fleet and commander of Naval Striking and Support Forces in Southern Europe, and he later became Bush's acting homeland security adviser.
Retired Navy Vice Adm. PGardner Howe speaks in Ponte Vedra Beach, Fla., on March 10.
"Over the past four years, I've seen what is a clear manipulation of our military to serve his personal needs," Abbot said.
In the 2016 election, dozens of former Republican senior national security officials came out against Trump and became known as "Never Trump" Republicans.
Many were blacklisted for jobs in the Trump administration for having signed the letters. »