Detectives are linking two attacks on a Northamptonshire pub which started when a gang smashed up the bar, and ended some hours later in an arson attack.
Up to 10 men burst into the Silver Horse public house in Goldings Road at about 2345 BST on Sunday.
The pub was severely damaged, but staff were unhurt, although badly shaken.
Four men were arrested are being questioned by Northamptonshire Police.
Later, at about 0345 BST on Monday, police and firefighters were called back to the pub after an arson attack.
Six fire engines were called to the scene and took an hour and twenty minutes to bring the blaze under control.
The two incidents are being linked and detectives have appealed for any witnesses to come forward.