On April 21, Secretary of State Cyrus R. Vance sent to Congress the Carter administration's legislative plan to repair the "vital" but strained security relationship with Turkey. The following morning, three angry pro-Greek lawmakers warned President Carter, Vance and presidential adviser Zbigniew Brzenzinski in a confidential White House meeting that a bloody battle would erupt unless the plan were watered down.

When Senate and House foreign policy committees finished markup sessions last week on the $3.1 billion foreign military assistance bill, two of the three points of the administration's Turkish proposal were missing. After top-level deliberations, Carter had backed down rater than risk the fight in Congress.

The power play in Turkish policy by House Democratic Whip John Brademas (D-Md.) is a notable but by no means isolated example of the continuing independence of Congress on foreign policy issues. Despite the coming to power of a Democratic President, last week's military aid markups showed Congress still has ideas of its own.

In maneuvering during the committee markup sessions - which often dictate the final form of legislation - the lawmakers took the bit in their teeth on several important subjects of intense interest to their constituencies at home as well as naions abroad.

On the issue of aid in Southern Africa, a House committee rewrote a major program to orient it to black states rather than white-ruled Rhodesia. On control of conventional arms, a Senate subcommittee weighed in with a policy pronouncement on behalf of Israel. As in the Greek-Turkish controversy, the interests and emotions of politically important American groups were involved in both these cases.

The Turkish aid problem and attitudes about it were legacies of the 1974 legislative rebellion against then Secretary of State Henry A. Kissinger. Against his advice, Congress cut off military aid and embargoed arms sales to Turkey as pressure on that country following its invasion of Cyprus and because the Turkish use of U.S. arms violated the terms of sale.

In retaliation, Turkey shut down important U.S. military and intelligence installations, reassessed its status as a North Atlantic Treaty Organization ally and improved relations with Soviet Union, Greek Americans cheered the U.S. action, but the executive branch, many diplomats, and an increasing number of members of Congress considered the 1974 embargo a serious mistake.

Carter's three-point plan, intended to repair some of the damage, called for:

Permitting up to $175 million in government-to-government arms sales in the next fiscal year.

Allowing extra Turkish purchases above this limit to complete previously signed contracts for 40 F-4 Phantom jets at a cost of $320 million.

A congressional acknowledgement, far short of formal approval that would be sought later, of the $1 billion long-term bases agreement negotiated with Turkey by the Ford administration.

According to informed sources, the three lawmakers reminded Carter on April 22 of his campaign oratory last year courting votes in the Greek community, and threatened to make his campaign statements the centerpiece of a politically embarrassing debate. Moreover, Carter reportedly was told, "You will need us on the Panaman Canal," suggesting that one controversial foreign policy initiative was to be held ransom for another.

An experienced head-counter in the House estimated that pro-Greek forces would have been able to muster no more than six votes in 37-member International Relations Committee and 100 votes on the House floor had Carter led a serious fight for his three-part Turkish package.

In the Senate, Humphrey said, Carter might have won had he chosen to do battle. However, the veteran warrior counseled the White House, "Don't break your pick on this one." While formally standing by all three proposals, Vance notified senior lawmakers last week that the administration would not mount a major effort for points two and three. In return, the pro-Greek forces acquiesced in the $175 million sales limit - but nothing more.

As the Greek-Turkish maneuvering illustrates, congressional direction of U.S. policy can be particularly important when the interests or emotions of U.S. ethnic or minority groups are involved. During last week's deliberations on the military aid bill:

A proposed $100 million U.S. contribution to a planned "transition" fund for use in white-ruled Rhodesia was transformed by the House International Relations Committee into a $100 million U.S. aid program for black-ruled "front line" African countries on Rhodesia's borders. The change was engineered by Rep. Charles C. Diggs Jr., a black Democrat from Detroit who is chairman of the African subcommittee and whose private office - a small museum of African artifacts and autographed pictures of African leaders - attests to his standing as one of the leading congressional experts on that continent.

Although a shift began in the final months of Kissinger's tenure, the House committee action implies a fundamental turnabout in U.S. policy in southern African from identification mostly with whites to identification with blacks. Party of the underlying politics involved is the rising consciousness among American blacks of their African "roots" and the growing foreign policy interest of such organizations as the NAACP and Urban League.

The Senate subcommittee, is one of many actions taken in secret under the cloak of "national security," adopted with little discussion a complex and highly detailed amendment placing Congress on record behind Israel in a struggle with the executive branch over arms procurement policies. Sources said the amendment was handed to Sen. Clifford Case (R-N.J.), who often leads legislative fights for Israel by committee staff aide Stephen Bryen.

The Carter administration's plans for a new arms export policy, recently disclosed to Congress in confidential briefings, include major limitations on "co-production" of sophisticated U.S. weaponry in foreign countries. Such a worldwide policy would be a major hurdle for Israel's proposal to manufacture F-16 warplanes and other highly advanced U.S. weapons, and has brought expressions of alarm from the Israeli Cabinet.

The amendment places Congress on record behind Israel "co-production" of weapons systems as well as U.S. subcontracting to Israel for manufacture of components. It also calls for a U.S. weapons systems. If enacted into law, this would b U.S. preference to Israel for repair and overhaul of U.S. weapon systems. If enacted into law, this would be a directive of special consideration to Israel in the weapons field. Humphrey suggested in an interview that the amendment may be withdrawn, however, if the executive branch voluntarily adopts a satisfactory policy toward Israelis arms in the next few days.

Bryen said an "expert" whom he would not name helped his draft the lengthy amendment on behalf of Case. The staff aide said the amendment did not originate with the Israeli government or a pro-Israeli lobby group.

Israel and the Arab countries just around it have become the main benefeciaries of the military assistance bill since the decline of U.S. involvement in Asia.

Subtracting the $300 million loan to Portugal, submitted to Congress separately and added to the bill for legislative convenience, the U.S. military and "security supporting" assistance bill authorizes worldwide outlays of $2.8 billion. Of this $1.33 billion, or about half, is earmarked for Israel on an outlay basis (on a nominal loan basis the Israeli figure is even higher). Adding Egypt ($750 million), Jordan ($155 million) and Syria ($80 million) brings the Middle East outlay total to $2.3 billion - leaving $300 million for the rest of the world.

"We're still living in the shadow of the Nixon excesses and the Vietnam war," said Humphrey in explanation of Congress' continuing determination to put its own stamp on foreign policy through legislation and the power of the purse. "Things have changed some but not much," he said.

"Nothing has changed," groaned Rep. Helen S. Meyner (D-N.J.) following a markup session of the House committee. Although President Carter espouses major changes in arms and military policies abroad, the military assistance bill now before Congress was written by the Ford administration and altered little by the new policymakers.

The State and Defense officials defending the bill in committee sessions were mostly holdovers from the past. In the House committee the executive branch lobbyists seemed still to work most closely with Republicans.

Far from loosening their control over programs and policies abroad, the congressional committees adopted amendments which would tighten their hold.

A House committee amendment would require congressional review whenever U.S. arms originally sold to one country are later transferred to another country. An amendment accepted for further Senate consideration would require country-by-country arms sales programs to be submitted to Congress yearly - and require congressional approval to revise this upward during the year. Albert (Pete) Lakeland, a staff aide to Sen. Jacob K. Javits (R-N.Y.), conceived and drew up the latter plan.

While a few lawmakers become deeply involved in politically sensitive issues such as Greece and Turkey, most of the new congressional strings on arms sales, military advisers and other overseas transactions are watched by staff aides. Most elected legislators are too busy to consider such details.

Te House International Relations Committee staff has tripled since 1971, from 21 members then to 74 members now. This year, for the first time, regional and functional subcommittees held the hearings and made the initial decision on the military aid bill. On the better subcommittees, which have become increasingly important as legislative sub-units, representatives have become familiar with the countries whose fortunes they consider. "The fact that members of subcommittee know the names of the countries is an advance," said a veteran staff aide.

The Senate Foreign Relations Committee, once a backroom operation where a few key senators and secretaries of state shared confidences over bourbon and cigars, has move than doubled its staff, from 26 in 1971 to 61 staff members today. In the military aid markups last week, subcommittee staff placed 56 pages of proposed legislation and staff recommendations before every senator. The staff recommendations were rarely rejected.

"We've made a lot of work for ourselves," said Humphrey, who was the architect of last year's law tightening legislative control on arms sales and military advisory groups. Humphrey is wary of going too much deeper into the details of foreign policy in this era of congressional independence. "Senators don't have the time to read all these reports and it adds to work for the staffs. If we're not careful, pretty soon we'll have the staffs running the government," he said.