With no explanation, label each line with "O", "event-attack/battle/war/militaryconflict", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
The
fort
was
abandoned
around
the
time
of
Caesar
's
invasions
of
Britain
in
55
and
54
BC
and
may
have
been
attacked
by
the
Romans
,
if
the
burned
northern
gate
indicates
an
assault
rather
than
slighting
by
retreating
defenders
.
The:O
fort:O
was:O
abandoned:O
around:O
the:O
time:O
of:O
Caesar:event-attack/battle/war/militaryconflict
's:event-attack/battle/war/militaryconflict
invasions:event-attack/battle/war/militaryconflict
of:event-attack/battle/war/militaryconflict
Britain:event-attack/battle/war/militaryconflict
in:O
55:O
and:O
54:O
BC:O
and:O
may:O
have:O
been:O
attacked:O
by:O
the:O
Romans:O
,:O
if:O
the:O
burned:O
northern:O
gate:O
indicates:O
an:O
assault:O
rather:O
than:O
slighting:O
by:O
retreating:O
defenders:O
.:O