Robert Mugabe, the leader of the most militant wing of the guerrillas fighting for black-majority rule in Rhodesia, returned home from exile today in triumph, greeted by the largest political rally ever held in this country.

Before a crowd estimated at more than 200,000, Mugabe sharply attacked the temporary British colonial administration of Lord Soames, the governor. He thus brought home to the capital the war of words of the two have been conducting over the 1,000 miles separating Salisbury from Maputo, Mozambique, where Mugabe's Zimbabwe African National Union has had its headquarters.

The 51-year-old leftist leader said "ZANU has not had a fair deal at all." He specifically criticized Soames for:

Deploying Rhodesian forces and "auxiliary" troops loyal to his political opponent, former prime minister Abel Muzorewa, against Mugabe's guerrillas.

"Manipulating the political situation" to the disadvantage of ZANU, particularly citing the alleged British refusal to let him return earlier.

Allowing South African troops to remain in Rhodesia.

The crowd cheered its approval of each attack on the British, an indication that the political situation will heat up in the month before the British-supervised election of a black-majority government.

Mugabe also sought to reassure the country's white minority, saying that despite reports to the contrary he had no plans to seize land or businesses or to suppress religion.

The main message of the day, however, was the crowd. Estimates of its size ranged from a conservation one by the police of 150,000 to others of 250,000. It means that there were probably about as many people gathered for Mugabe in the Highfield black suburb of Salisbury as there are whites in the entire country.

The seven-year war fought by guerrillas led by Mugabe and his coleader in the Patriotic Front alliance, Joshua Nkomo, sought to wrest power from the whites, generally estimated to number around 220,000. An agreement reached in London last month among Britain and the warring sides officially ended the fighting and established the British in a transitional governmental role leading to elections Feb. 27 through 29 for an independent government.

At first Mugabe seemed to be taken aback by the size and ecstatic response of the crowd when he arrived to prolonged applause. It was the first time he had faced an audience in Rhodesia as leader of ZANU, since he only wrested control of the party from another rival, Ndabanigi Sithole, in 1975, shortly after being released from 10 years of detention and going into exile.

ZANU political and military leaders, including Mugabe's wife, Sally, led 20 minutes of rousing cheers for the leader, various heroes of the organization and for neighboring countries that had supported their fight.

The main cries from the "cheerleaders" were "Forward with Mugabe" and "Down with" Muzorewa or Smith, for Ian Smith, the white prime minister who illegally declared indepndence in 1965 to preserve white rule.

The size of the crowd is likely to give strong momentum to Mugabe's election drive. Since Rhodesia's black political parties have slowly emerged over recent years after being banned or harassed by the former Smith government, crowd sizes have played an important role in national political psychology.

Muzorewa, who has the support of the whites, had a rally at the same site three weeks ago attended by about 50,000.

Nkomo returned two weeks ago from three year's to a crowd estimated to range between 120,000 and 150,000. Today's police estimate was 150,000 but many observers put the crowd at more than 200,000 and said it was certainly larger than the previous record, about 170,000 who welcomed Muzorewa back to the country in 1977.

Mugabe's most telling remarks were directed at Lords Soames. He switched from Shona to English and spoke as if Soames were there.

"You have chosen to deploy the Rhodesian forces and neglected to deploy the Patriotic Front troops to bring in guerrillas who have not assembled," he said. "This is discrimination and it must stop."

"You have manipulated the political situation. . . to the disadvantage of ZANU," and delayed his return, Mugabe said, and then added to the cheers of the crowd, "But I am here now."

Mugabe also repeated an earlier threat that his assembled troops may be called to action, a move that could wreck the delicate election situation.

"As we have moved into assembly points, we can move out ot them," he said, referring to the 21,000 Patriotic Front troops who have assembled under the terms of the cease-fire.

Complaining about the activities of Muzorewa's auxiliaries, he said that if they "continue to harass our people, we will have no other alternative than to come to their defense."

The British administration maintains that Mugabe's forces are the main disruptive element in the ceasefire, thus necessitating action by the Rhodesian and auxiliary forces. British officials have admitted that Mugabe's return was linked to the release of ZANU dissidents held in Mozambique. They are scheduled to be freed Monday.

Earlier at a press conference at Salisbury airport, Mugabe took a more moderate tone, saying he would have to discuss these problems with Soames.

He stressed that whites had a role to play in an independent Zimbabwe that property would not be expropriated without compensaton and that a ZANU government intended to coexist with South Africa and not support elements seeking to overthrow the white-minority government there.