"First  of all, a statement from royalty." 
In the spirit of the way this phrase was understood by my revered father-in-law, the Rebbe [Rayatz],  let us open with one of his brief teachings.
In the maamar for Pesach  which begins with the words,  Be'etzem HaYom hazeh yatzu kol tzivos HaShem meiEretz Mitzrayim ("On that very day it came to pass, that all the hosts of G-d went out of the Land of Egypt"), the Rebbe [Rayatz] explains why at the time of the Exodus the Jewish people are called tzivos HaShem - "the hosts (lit., 'the armies') of G-d."
At that time, he explains, their divine service was not merely that of a servant (avodas eved), which entails toil and exertion but not self-sacrifice. Rather, they had attained the level of an army, standing guard at their respective posts with self- sacrifice.
"They  were vigilant in being distinguished  there, changing neither their names nor their language nor their garb;  they stood their ground with the utmost fortitude."
In a recent letter, someone pointed out that this teaching would appear to contradict another teaching of the Sages - that [on the eve of the Exodus, the charge was leveled in the Heavenly Court that]  "those [i.e., the Egyptians] are idolaters, but so, too, are these [i.e., the Children of Israel]."
On a straightforward level, one could resolve this seeming contradiction by noting that the latter quotation refers not to actual idolatry but to their belief in a compound Divinity. 
Such a belief was not then forbidden to the Jewish people, since at the time of the Exodus, before the Giving of the Torah, they were classified as "descendants of Noah."
(This is explained in Sefer HaMitzvos by the Tzemach Tzedek, in the discourse [on the Unity of G-d] entitled Mitzvas Achdus HaShem. )
At the level of pnimiyus, the innermost dimension of the Torah, this solution is not satisfactory.
It does not appear reasonable that the Torah should praise the Jewish people by referring to them as an army that goes to the point of self-sacrifice in guarding its faith in G-d, when the subject of that faith is [not a Unity but] a compound Divinity.
We must therefore conclude that their faith was complete.
(Witness the statement of Rashi:  "They did not say, 'How shall we go out into the wilderness without provisions?' Rather, they believed and went forth.")
At the same time, however, the sitra achra caused alien thoughts, doubts that questioned their faith in G-d, to fall into their minds. (This is explained in Tanya. )
This alien intervention did not (G-d forbid) weaken the vigor of the faith that welled from the essence of their souls.
In this connection one is reminded of the individual who entered the study of the Tzemach Tzedek and complained that his head was occasionally visited by doubting thoughts.
"Why should that worry you?" asked the Tzemach Tzedek. "But Rebbe," he exclaimed, "I'm a Jew!" "Then everything's in order...," responded the Tzemach Tzedek.
This exchange recalls the situation of our forefathers at the time of the Exodus.
- (Back to text) This sichah was delivered by the Rebbe in 5710 , on the eve of Beis Iyar, [the date on which the Rebbe Maharash was born in 1834].
- (Back to text) In the Heb. original, pos'chin bidvar malchus.
- (Back to text) See the sichah of Lag BaOmer, 5708  (which appears in the original Heb./Yid. edition of Likkutei Dibburim, Vol. III, p. 514a) [and in its Eng. translation: Vol. IV, ch. 30]; and the sichah of Yud-Beis Tammuz, 5708  (which appears in Sefer HaMaamarim 5709 , p. 199).
- (Back to text) See Sefer HaMaamarim 5710 , p. 171ff.
- (Back to text) Shmos 12:41.
- (Back to text) Sefer HaMaamarim 5710 , p. 176.
- (Back to text) The term is borrowed from the Haggadah for Pesach.
- (Back to text) See Mechilta, Parshas Bo 12:6; Pesikta Zutrasi, Parshas Va'eira 6:6; et al.
- (Back to text) See Zohar II, 170b; Mechilta, Parshas Beshalach 14:28; Yalkut Reuveni, loc. cit., sec. 27.
- (Back to text) In the original, shituf.
- (Back to text) [The above is the subtitle for the work entitled] Derech Mitzvosecha; see there, p. 59b ff. See also Likkutei Sichos, Vol. XXI, p. 41, footnote 36, and sources listed there.
- (Back to text) See his commentary on Shmos 12:39, and also on Devarim 32:10.
- (Back to text) End of ch. 29.