ANTI-AIRCRAFT DEFENCE The problem of anti-aircraft defence enters into all forms of action against a well-equipped enemy, and anti-aircraft artillery is now provided in most armies. Anti-aircraft artillery may act in co-operation with fighting aircraft, when its main task will be to assist them by breaking up formations of hostile aircraft and by indicating their whereabouts by shooting at them. It may also act independently; its role is then to destroy hostile aeroplanes and to deny them opportunities of bombing and detailed observa tion. Anti-aircraft artillery will usually be employed for the pro tection of columns on the march and of forward areas when an army has deployed. Owing to the great radius of action of modern aircraft, anti-aircraft artillery has also to be provided for the air defence of bases, headquarters and other important points on the lines of communication of an army. Searchlights are required in rear areas to enable the guns to engage hostile aircraft at night.