OPINION
RABINOWITZ, Justice.This appeal is taken from judgments and commitments which were entered by the superior court after the matters had been remanded from this court pursuant to our opinion in Cleary v. State, 548 P.2d 952 (Alaska 1976).
Appellant Michael Cleary was indicted on January 30, 1975, for four counts of robbery, in violation of AS 11.15.240,1 and in a separate indictment was charged with one count of attempted robbery and one count of robbery. The robberies spanned a period of time from January 9, 1975, to January 25, 1975. Cleary was also under indictment *375in the United States District Court for armed bank robbery. In March of 1975 Cleary pled guilty to the federal charge and was sentenced to a term of five years.
On May 16, 1975, Cleary pled guilty to the four counts of robbery and to the additional robbery count contained in the separate indictment. On July 21,1975, Superior Court Judge Kalamarides sentenced Cleary to 10 years on each of the four robbery counts (in superior court No. 75-617 Cr.) and 10 years on the separate robbery count (in superior court No. 75-586). The sentences on the four robbery counts (No. 75-617 Cr.) were to run concurrently with each other and consecutively to both the federal sentence and the 10-year sentence which had been imposed on the separate state robbery charge. Thus, Judge Kalamarides sentenced Cleary to 20 years to follow the 5-year federal sentence. The sentences were appealed to this court and the matter was thereafter reversed and remanded to the superior court with instructions to vacate the sentences imposed and to resen-tence Cleary in conformity with our opinion in Cleary v. State, 548 P.2d 952 (Alaska 1976).
In our previous Cleary opinion we reiterated our view that we consider robbery among the most serious crimes2 and that:
Conduct such as that engaged in by Cleary calls for lengthy incarceration. With reference to the criteria enunciated in Chaney [State v. Chaney, Alaska, 477 P.2d 441], a substantial sanction is necessary to express the community’s condemnation of such behavior so as to deter other members of the community from engaging in similar conduct. In addition, a long period of imprisonment unequivocally brings home to Cleary the seriousness of his dangerously unlawful conduct while preventing him from engaging in criminal conduct during the period of confinement.3
After reviewing all aspects of the record in Cleary, we concluded that the superior court properly rejected the district attorney’s recommended sentence which would have enabled Cleary to return to the community upon completion of service of his federal sentence. More particularly, we said in Cleary that:
In order to effectuate the goals enunciated in the State constitution, we think it was appropriate for the superior court to impose a sentence which would run consecutively to the federal sentence. It does not appear to us, however, that the principle of public protection requires Cleary’s potential incarceration for an additional twenty years.4
Upon remand the matter was assigned to Superior Court Judge C. J. Occhipinti. During the hearing on resentencing, at the superior court’s insistence, counsel for the state recommended a sentence of 10 years imprisonment as to each of the five state robbery counts, all to be served concurrently with each other and consecutively to the federal sentence. At this sentencing hearing, the state did not produce any additional evidence. Although Cleary did not present witnesses either, he made a statement concerning his present rehabilitation program in a federal penitentiary. Counsel for Cleary recommended 7½ years consecutive to the 5-year federal sentence. After taking the matter under advisement, the superior court sentenced Cleary to a 10-year sentence in No. 75-536 Cr. and 20 years on each of the four robbery counts in No. 75-617 Cr.; all sentences were made concurrent with each other; the 20-year sentences were made to run consecutively to *376the federal sentence, while the 10-year sentence in No. 75-536 Cr. was made concurrent with the federal sentence.5 This second sentence appeal followed.
We have concluded that the 20-year sentences imposed by the superior court as to each of the four robbery counts in No. 75-617 Cr. are illegal sentences and therefore must be vacated. Cleary was indicted on, and pled guilty to, four violations of AS 11.15.240 for which the maximum sentence is 15 years.6 In order for the superior court to have sentenced Cleary under AS 11.15.-295, the state must have charged and proven that a firearm was used during the commission of the crimes.7 Of controlling significance here is that Cleary pled guilty only to violations of AS 11.15.240. In this appeal, the state concedes that the sentences imposed by the superior court on the four robbery counts in No. 75-617 Cr. are “clearly illegal, and should be reversed and remanded for resentencing.”
We now turn to the disposition which should be made upon our second remand of the four robbery counts in No. 75-617 Cr. Cleary was indicted on, and pled guilty to, four violations of AS 11.15.-240 for which the maximum sentence is 15 years. Our re-examination of the record in the case at bar, in light of our initial decision in Cleary v. State, 548 P.2d 952 (Alaska 1976), persuades us that an appropriate sentence for these, four robbery counts would be one that substantially parallels the recommendation made by counsel for the prosecution at the sentencing proceedings which were conducted after our initial remand of this matter. More particularly, we are in agreement with the state’s recommendation that a sentence of 10 years imprisonment as to each of four robbery counts in No. 75-617 Cr., all to be served concurrently with each other and consecutively to the federal sentence, is an appropriate sentence under our decision in State v. Salinas, 362 P.2d 298, 301 (Alaska 1961), and the sentencing objectives articulated in State v. Chaney, 477 P.2d 441 (Alaska 1970), and its progeny.
One question remaining is whether the 10-year sentence in No. 75-536 Cr., which, according to the judgment and commitment in the matter, was to run concurrently with the 5-year federal sentence, is excessive. In our view, the superior court was not “clearly mistaken” in imposing a 10-year sentence in No. 75-536 Cr., whether the sentence is to be served concurrently with, or consecutively to, the federal sentence.8 In light of the seriousness of the offense, the record in this case, and what we consider to be an appropriate sentence as to the four robbery convictions in superi- or court No. 75-617 Cr., we conclude that the superior court’s sentence in No. 75-536 Cr. was not excessive and is affirmed.9
Because of the sentence imposed on our first remand, we consider it necessary *377to discuss an additional facet of this appeal. As mentioned previously, the only new fact elicited at the sentencing hearing on remand was that Cleary was presently enrolled in a rehabilitation program in the Oxford Federal Penitentiary in Madison, Wisconsin. Nevertheless, the superior court imposed sentences which were equivalent in length to the sentences this court had previously held excessive and had ordered vacated in Cleary v. State, 548 P.2d 952 (Alaska 1976). In regard to the obligation of the trial court upon remand of a matter from this court, we observed in State v. Salinas, 362 P.2d 298, 301 (Alaska 1961):
*376A person who uses or carries a firearm during the commission of a robbery, assault, murder, rape, burglary, or kidnapping is guilty of a felony and upon conviction for a first offense is punishable by imprisonment for not less than 10 years. Upon conviction for a second or subsequent offense in violation of this section, the offender shall be imprisoned for not less than 25 years.
*377It is our view that upon remand of a case by this court it becomes the duty of the lower court to obey the mandate and render judgment in conformity. This rule is supported by the overwhelming weight of authority and is based on the policy that litigation must be finally ended.10 (footnotes omitted)
Thus, we take this occasion to express our disapproval of the superior court’s imposition upon remand of 20-year sentences on each of the four robbery counts in No. 75-617 Cr. which were made to run consecutively to the 5-year federal sentence. The superior court’s sentence with respect to the four robbery counts was inconsistent with the holding of Cleary v. State, 548 P.2d 952 (Alaska 1976), and this court’s mandate issued pursuant thereto as well as violative of the principles articulated in State v. Salinas, 362 P.2d 298, 301 (Alaska 1961).
The judgment and commitment in No. 75-536 Cr. is affirmed. The sentence in No. 75-617 Cr. is vacated and remanded for sentencing in conformity with this opinion.
. AS 11.15.240 provides:
A person who, by force or violence, or by putting in fear, steals or takes anything of value from the person of another is guilty of robbery, and is punishable by imprisonment in the penitentiary for not more than 15 years nor less than one year.
. In Cleary v. State, 548 P,2d 952, 955 (Alaska 1976), we further elaborated upon our view of robbery and stated that:
This court, without question, considers robbery to be ‘among the most serious crimes.’ We note that Cleary was involved in six robberies: furthermore, he used a handgun in each instance. As observed by a recent article on sentence review in Alaska, ‘the use of weapons aggravates the nature of the crime’. Although nobody was injured by Cleary’s actions, we think it is ‘appropriate to take into consideration the potential injury to the victim in arriving at a proper sentence.’ (footnotes omitted)
. Id, at 955.
. Id. at 956.
. We note that there is a conflict between the superior court’s Sentence Memorandum and the Judgment and Commitment which was entered in No. 75-536 Cr. In its decision in the Sentence Memorandum, the superior court indicated that all of the state sentences would be made to run consecutive to the federal sentence.
On the same day that a notice of appeal was filed in these matters, counsel for Cleary filed in the superior court a motion for clarification in which the superior court was asked to clarify “ . . . whether the sentence in Case No. 75-536 shall be served concurrently or consecutively to the sentence imposed in Federal Court.” The records of the superior court reflect that no determination has yet been made on the motion.
. For the text of AS 11.15.240, see note 1, supra.
. AS 11.15.295 provides:
. See note 5, supra.
. In Marks v. State, 557 P.2d 1136 (Alaska 1976), we approved a 5-year sentence for a single count of robbery carried out with an unloaded handgun. This court has previously approved 10-year sentences for robbery in Hix-on v. State, 508 P.2d 526 (Alaska 1973), and Robinson v. State, 492 P.2d 106 (Alaska 1971).
. See United States v. O'Brien, 391 U.S. 367, 377, 88 S.Ct. 1673, 1679, 20 L.Ed.2d 672, 680 (1968); Lichter v. United States, 334 U.S. 742, 756 n. 4, 68 S.Ct. 1294, 1302, 92 L.Ed. 1694, 1711 n. 4 (1948); United States v. Crocker, 294 F.Supp. 776, 777 (D.Minn.1969). Compare ABA Project on Minimum Standards for Criminal Justice, Standards Relating to Appellate Review of Sentences, Standard 3.4 at 66 (Approved Draft 1968).