In the absence of cover, an advance in quick time will be possible only at long ranges unless the hostile fire can be kept down by fire from enfilading or commanding positions. Skirmish lines advancing without fire support over ground devoid of cover, begin to suffer appreciable losses at 1000 m. The more effective the hostile fire, the more pressing the necessity of diminishing, as far as this is possible, the periods of time during which the skirmishers present their whole bodies as targets to the enemy. This leads in itself[88] to an =advance by rushes=, since the whole distance separating the advancing line from the enemy cannot be covered in one rush. Double time may be employed by a skirmish line when it becomes necessary to reinforce an advancing firing line quickly, to forestall the enemy in reaching a certain point, or in moving under fire, from the covered fire position occupied, to another position. It is impossible to prescribe definitely and for all cases at what ranges the advance by rushes should be taken up and when fire should be opened in advancing by rushes, since it depends upon the intensity of the hostile fire. [88] KUNZ, _Kriegsgeschichtliche Beispiele_, 14, pp. 40, 48 and 77. The assailant will, in the first place, endeavor to advance without firing, in order to reach those ranges quickly at which his fire will begin to be effective against the well-covered targets of the defender. The skirmishers advance in strong detachments, by rushes of the greatest possible length, taking short breathing spells at each halt. Very soon, however, the hostile fire makes this advance impossible. A fire fight of variable duration must first make a further advance possible by silencing the fire of the defender. In a serious infantry engagement every step forward must be purchased by the fire of the attacking infantry. The attacker will, in exceptional cases only, continue his advance in long lines, although this must appear desirable to him, for almost invariably only a part of his force will still be able to gain ground to the front when supported by the fire of neighboring detachments. Favorable local conditions, insignificant losses, and, above all, the personality of the commander will embue a force with the determination to advance. Time Required for Making a Rush. Strength of the Force Making the Rush. The squad requires 5-6, the platoon at war strength about 10-15 seconds preparation for making a rush. To cover 80 m., requires 26-30 seconds; „ „ 40 „ „ 17-20 „ „ „ 25 „ „ 10-15 „