appointed time, (+) army, (+) battle, company, host, service, soldiers, waiting upon, war(-fare)

“Captain” From Boyd’s Bible Dictionary:

(head). Title for a leader of a band of ten, fifty, hundred or thousand (Deut. 1:15; Josh. 10:24; Judg. 11:6,11). Also a civic meaning (Isa. 1:10; 3:3). “Captain of the Guard” (Acts 28:16), was commander of the Praetorian troop of Rome. “Captain of the Temple” (Acts 4:1), was chief of the Temple watchmen.

“Army” From Boyd’s Bible Dictionary:

Hebrew males twenty years old and upward subject to military duty (Num. 1:2-3). Tribes formed army divisions. Numerated by hundreds and thousands, each with captains (Num. 31:14). Kings had body-guards (1 Sam. 13:2; 25:13). Later, a standing army formed (2 Chron. 25:6). No cavalry till Solomon’s time. War declared and exempts used as (Deut. 20:1-14; 24:5). In N. T. Roman army composed of legions, with chief captains (Acts 21:31); tents of legions, or cohorts, and bands (Acts 10:1); maniples, or thirds of legions; centuries, 100 men each and two to a maniple. Captain of a 100 called a Centurion (Matt. 8:5; 27:54).

“Captain” From Concise Bible Dictionary:

In the Old Testament this word is used for one filling any office of rule or command: as the head of a tribe (Num. 2:3-29); commander of an army, and so forth. The person who appeared to Joshua as “a man” declared himself to be “captain of the Lord’s host.” He told Joshua to remove his shoes from his feet, for the ground was holy, evincing that he was God’s representative to lead their warfare (Josh. 5:14-15). In the New Testament the Lord is called “Captain” of our salvation, ἀρχηγός, “chief leader” (Heb. 2:10).
There was also a “CAPTAIN OF THE TEMPLE,” στρατηγός (Luke 22:4, 52; Acts 4:1; Acts 5:24, 26). This word is literally “the leader of an army”; it is also applied to magistrates (Acts 16:20), but the captain of the temple was set not over the soldiers, but over the priests and Levites: (Compare Num. 32; 1 Chron. 9:11; Jer. 20:1).
THE CHIEF CAPTAIN or HIGH CAPTAIN is χιλίαρχος, lit. “Captain of a thousand,” applied to the chief of the soldiers in Jerusalem (Acts 21-25).
CAPTAIN OF THE GUARD (Acts 28:16), is στρατοπεδάρχης, properly “commander of a camp,” but here the prefect of the Prætorian Guard, an officer to whom state prisoners were entrusted at Rome.

“Army” From Concise Bible Dictionary:

It must be remembered that Israel were the hosts of Jehovah, keeping His charge and fighting His battles (Ex. 12:41; Josh. 5:14). It appears that all who reached the age of twenty years were contemplated as able to bear arms (Num. 1:3); and they marched and encamped in 4 divisions of 3 tribes each, with a captain over every tribe. The subdivisions were into thousands and hundreds (Num. 31:14), and into families (Josh. 7:17). There were also trumpet calls (Num. 10:9, compare 1 Cor. 14:8), and all the appearance of careful organization. Until the time of the kings this natural or tribal organization seems to have been usual, but in the time of Saul there was a body guard (1 Sam. 13:2), and a captain of the host (1 Sam. 17:55). In David’s days those heroes who were with him in the cave of Adullam formed the nucleus of his “mighty men” (2 Sam. 23:8-39). They were devoted to the service of God’s king. David afterward organized a monthly militia of 24,000 men under 12 captains (1 Chron. 27:1-15).
The general gradation of ranks was into privates; “men of war”; officers; Solomon’s “servants”; captains or “princes”; and others variously described as head captains, or knights or staff officers; with rulers of his chariots and his horsemen (1 Kings 9:22). It may be noticed that horses having been forbidden (Deut. 17:16), it was not until Solomon’s time that this was organized, though David had reserved horses for a hundred chariots from the spoil of the Syrians (2 Sam. 8:4). Solomon, trading with Egypt (1 Kings 10:28-29), enlarged their number until the force amounted to 1,400 chariots, and 12,000 horsemen (1 Kings 10:26; 2 Chron. 1:14). Every able man being a soldier gave David the immense army of 1,570,000 men that “drew sword” (1 Chron. 21:5). After the division, Judah under Abijah had an army of 400,000 “valiant men,” and Israel at the same time of 800,000 “chosen men.” Afterward Asa had 580,000 “mighty men of valor”; and Jehoshaphat, who had waxed great exceedingly, had as many as 1,160,000 men, besides those left in the fenced cities (2 Chron. 17:14-19).
In the New Testament a few references are made to the Roman army. A “Legion” was a body that contained within itself all the gradations of the army. It might be called under the empire, in round numbers, a force of not more than 6,000 men. Every legion at times contained 10 cohorts of 600 each; every cohort 3 maniples of 200; and every maniple 2 centuries of 100: hence the name of centurion or commander of 100 men, as found in Acts 10:1,22. Each legion was presided over by 6 chiefs, χιλίαρχος, each commanding 1,000 men, mostly translated “chief captain,” as in Acts 21:31-37; it is “high captain” in Mark 6:21; and “captain” in John 18:12 and Revelation 19:18. A cohort, σπεῖρα, is translated “band” in Acts 10:1; 21:31. A “quaternion” embraced 4 soldiers (Acts 12:4).
The head quarters of the Roman troops was at Cæsarea, with a cohort at Jerusalem; but at the time of the feast, when, alas, the mutinous disposition of the Jews was sure to appear, additional troops were present in the city but without their standards of the eagle, which were especially obnoxious to the Jews. Though the Romans were God’s rod to punish them, their stiff necks could not bow, nor receive the punishment as from Jehovah.

Strong’s Dictionary of Hebrew Words:

Transliteration:
tsaba’
Phonic:
tsaw-baw’
Meaning:
or (feminine) tsbadah {tseb-aw-aw'}; from 6633; a mass of persons (or figuratively, things), especially reg. organized for war (an army); by implication, a campaign, literally or figuratively (specifically, hardship, worship)
KJV Usage:
appointed time, (+) army, (+) battle, company, host, service, soldiers, waiting upon, war(-fare)