In a military campaign, burning your boats or bridges would make escape or retreat impossible.
cross that bridge when you come to it
deal with a problem when and if it arises.
1998 - Spectator - As to what would happen to the case for non-proliferation when the Cold War was won, the allies would cross that bridge when they came to it which seemed at the time well beyond any foreseeable future.
hold no brief for
not support or argue in favour of
The brief referred to is the summary of the facts and legal points in a case given to a barrister to argue in court.
bright and early
very early in the morning
as bright as a button
intelligently alert and lively – informal
There is a play here on bright in its Old English sense of shiny (like a polished metal : button) and bright in its transferred sense of quick-witted, found since the mid 18th century.
the bright lights
the glamour and excitement of a big city
a clever person (often used ironically to or of a person who has done something you consider stupid) - British informal
bright young thing
a wealthy, pleasure loving and fashionable young person
The term was originally applied in the 1920s to a member of a young fashionable group of people noted for their exuberant and outrageous behaviour.
look on the bright side
be optimistic or cheerful in spite of difficulties.
bright-eyed and bushy-tailed
alert and lively and eager - informal
bring home the bacon
supply material provision or support
achieve success – informal
This phrase probably derives from the much earlier save your bacon, recorded from the mid 17th century. In early use bacon also referred to fresh pork, the meat most readily available to rural people.
bring the house down
make an audience respond with great enthusiasm, especially as shown by their laughter or applause
bring something home to someone
make someone realize the full significance of something.
bring someone to book
bring someone to justice or punish someone.
the British disease
a problem or failing supposed to be characteristically British especially (formerly) a proneness to industrial unrest - informal
broad in the beam
fat round the hips – informal
A beam was one of the horizontal transverse timbers in a wooden ship and so the word came to refer to a ship's breadth at its widest point. It is from this sense that the current meaning of broad in the beam developed.
in broad daylight
used generally to express surprise or outrage at someone's daring to carry out a particular act, especially a crime, during the day, when anyone could see it.
it is as broad as it is long
there's no significant difference between two possible alternatives - informal