=180.= Sentinels salute, in accordance with the foregoing rules, all persons and parties entitled to compliments from the guards (Pars. 224, 227, and 228); officers of the Army, Navy, and Marine Corps; military and naval officers of foreign powers; officers of volunteers and militia officers when in uniform. =181.= A sentinel salutes as just prescribed when an officer comes on his post; if the officer holds communication with the sentinel, the sentinel again salutes when the officer leaves him. During the hours when challenging is prescribed, the first salute is given as soon as the officer has been duly recognized and advanced. A mounted sentinel armed with a rifle or pistol, or a dismounted sentinel armed with a pistol, does not salute after challenging. He stands at advance rifle or raise pistol until the officer passes. =182.= In case of the approach of an armed party of the guard, the sentinel will halt when it is about 30 paces from him, facing toward the party with his piece at the right shoulder. If not himself relieved, he will, as the party passes, place himself so that the party will pass in front of him; he resumes walking his post when the party has reached six paces beyond him. =183.= An officer is entitled to the compliments prescribed, whether in uniform or not. =184.= A sentinel in communication with an officer will not interrupt the conversation to salute. In the case of seniors the officer will salute, whereupon the sentinel will salute. =185.= When the flag is being lowered at retreat, a sentinel on post and in view of the flag will face the flag, and, at the first note of the Star-Spangled Banner or =to the color= will come to a present arms. At the sounding of the last note he will resume walking his post. No. 12: =To be especially watchful at night and during the time for challenging, to challenge all persons on or near my post, and to allow no one to pass without proper authority.= =186.= During challenging hours, if a sentinel sees any person or party on or near his post, he will advance rapidly along his post toward such person or party and when within about 30 yards will challenge sharply, "=Halt, who is there?=" He will place himself in the best possible position to receive or, if necessary, to arrest the person or party. =187.= In case a mounted party be challenged, the sentinel will call, "=Halt, Dismount. Who is there?=" =188.= The sentinel will permit only one of any party to approach him for the purpose of giving the countersign (Pars. 200 to 217), or, if no countersign be used, of being duly recognized. When this is done the whole party is advanced, i. e., allowed to pass.