The North Atlantic Treaty Organization was founded in April of 1949 by a country not on the European continent, the United States, and eleven subordinates which had fought on both sides of the World War that had ended four years earlier: Belgium, Britain, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway and Portugal. Greece and Turkey were added in 1952 after their service in the Korean War and West Germany joined in 1955.
Five days after the inclusion of the Federal Republic of Germany on May 9, in contravention of the 1945 Potsdam Agreement between Britain, the U.S. and the Soviet Union which explicitly demanded and meticulously detailed plans for the demilitarization of Germany, the Soviet Union established the Warsaw Treaty Organization (Warsaw Pact) in response. Fellow members were Albania, Bulgaria, Czechoslovakia, the German Democratic Republic (East Germany), Hungary, Poland and Romania. Albania formally withdrew in 1968, though it had not been a participating member since the early 1960s, and Romania had been a member in name only for at least twenty years before the pact’s formal disbandment.
With the accession of Spain into the "military alliance of democratic states in Europe and North America" in 1982 the U.S.-led military bloc grew from its original 12 to 16 members. By that time the Warsaw Pact had shrunk from eight to seven members and some of the remaining ones were only selectively involved.
NATO had regularly conducted large-scale military exercises in alleged defense of Norway, Denmark and other members, but never deployed forces or conducted operations outside member states’ territories, counting on the thousands of American nuclear warheads in European NATO states to respond to the Warsaw Pact’s conventional military superiority in the event of armed confrontation. 
Military forces from the Warsaw Pact intervened in Czechoslovakia in 1968 and in the early 1980s it appeared they might do so again in Poland, and the Soviet Union sent troops to Hungary in 1956 after Prime Minister Imre Nagy withdrew his nation from the Warsaw Pact.
The Soviet Union’s justification for those actions was that nations in Eastern Europe gravitating toward the West could be transformed into sites from which NATO, and especially its dominant member the U.S., would present a military threat on or near its borders.
In 1999, eight years after the formal dissolution of the Warsaw Pact and the fragmentation of the Soviet Union itself, the Czech Republic, Hungary and Poland were brought into NATO as full members during the bloc’s fiftieth anniversary summit in Washington, DC, while NATO was conducting its first large-scale military operation outside the territory of its member states and its first major armed conflict: The almost three-month Operation Allied Force air war against Yugoslavia, which had not been a member of either Cold War military alliance.
The accession of three former Warsaw Pact nations in 1999 was the largest one-time expansion in NATO’s history. Five years later at the Istanbul summit seven new members were inducted, six former Warsaw Pact countries, including three ex-Soviet republics, and a former federal republic of Yugoslavia: Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia.
With the earlier absorption of East Germany into NATO with German reunification in 1990, by 2004 every member of the erstwhile Warsaw Pact outside the Soviet Union except short-term member Albania had been brought into the Western military alliance. Albania was incorporated into NATO at the Strasbourg-Kehl summit last year.
The worst suspicions harbored east of the Cold War divide had been confirmed. Not only have all of the Soviet Union’s previous allies in Eastern Europe been recruited into a Washington-dominated military bloc that for eleven years has been actively waging wars in Europe and beyond Europe in Asia, but territory of what had been the Soviet Union itself now contains a NATO air base (Lithuania) and a cyber warfare center (Estonia).
Once Soviet Republics like Ukraine, Georgia, Azerbaijan and Armenia are being actively pursued by NATO, which has held military exercises in those countries.
In 2007 NATO selected the Papa Air Base in Hungary for its first Strategic Airlift Capability (SAC) operation in support of the wars in Afghanistan and Iraq (for the present). In the same year the Alliance announced it would open its first training center in a former Warsaw Pact country, in the Polish city of Bydgoszcz.
Starting the year after they were admitted as full NATO members, Bulgaria and Romania were approached by the U.S. to offer the Pentagon access to several major military bases.  Both countries had turned their air bases over to Washington in late 2002 and early 2003 for the invasion of Iraq, but in 2005 and 2006 Secretary of State Condoleezza Rice signed formal agreements for the acquisition of military bases with Romania and Bulgaria, respectively. The Mihail Kogalniceanu Air Base and training and firing grounds in Babadag, Cincu and Smardan in Romania, and the Bezmer Air Base, the Graf Ignatievo Air Base and the Novo Selo Training Range in Bulgaria were locked into initial ten-year agreements. The Pentagon is not planning to leave, surely not after spending billions of dollars to modernize the facilities.
The deployment of between 5,000-10,000 U.S. troops to the bases at any one time is the first Pentagon presence in former Warsaw Pact nations. And the seven Bulgarian and Romanian installations are the first American military bases in any of those countries. Neither the troops nor the bases were the last.
The U.S. has moved its Joint Task Force-East, whose name alone indicates its purpose, to the Mihail Kogalniceanu Air Base in Romania, and in the words of the unit’s deputy commander in 2008, "We are building a permanent forward operating station here…." 
The worst fear of the Soviet Union during the Cold War years was not just of NATO in general but of the U.S. in particular moving its military personnel and hardware toward its borders. Anyone who experienced a nightmare of that occurring twenty years ago and only woke up decades later would have difficulty realizing it was no longer just a dream.
NATO is, simply put, the major mechanism for moving the U.S. military into the territory of what had been the Warsaw Pact. And the Soviet Union. Permanently and aggressively.
By 2006 the advance of the Pentagon into Eastern Europe under the banner of NATO had become apparent enough – inescapably so – that quite far from the continent a Chinese military analyst, Lin Zhiyuan, deputy office director of the World Military Affairs Research Department of the Chinese Academy of Military Sciences, wrote that "new military bases, airports and training bases will be built in Hungary, Romania, Poland, Bulgaria and other nations to ensure ‘gangways’ to some areas in the Middle East, Africa and Asia [for] possible military actions in the years ahead.” 
As a major American news agency described the plans in 2007, “The bases are part of an ambitious plan to shift EUCOM’s [European Command’s] fighting brigades from western Europe –” mostly Germany –” to forward bases closer to the Caucasus, the Balkans, the Middle East and Africa, for a quicker strike capability.”  
The Bezmer, Graf Ignatievo and Mihail Kogalniceanu air bases in Bulgaria and Romania are being upgraded to serve as part of a series of new American strategic air bases outside the U.S. Aimed toward the east and the south.
In Poland, the activation of an Advanced Patriot Capability-3 interceptor missile battery manned by at least 100 U.S. military personnel has been scheduled for later this month. The troops will be deployed only 35 miles from Russia’s isolated enclave of Kaliningrad and will be the first foreign forces stationed in that nation since the end of the Warsaw Pact.
They will not be the last. After U.S. President Barack Obama met with the leaders of eleven new Eastern European NATO states – Bulgaria, Croatia, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, Slovakia, and Slovenia – in Prague on April 8 following the signing of a Strategic Arms Reduction Treaty (START) II agreement with Russian President Dmitry Medvedev, Polish President Donald Tusk told reporters "From the perspective of [President Obama] and the U.S. the signing of the START 2 treaty has no influence on the work on the SM3 anti-missile shield." 
Tusk was not speaking of the short- to medium-range Patriots missiles that may arrive in his country any day, but of Standard Missile-3 longer-range anti-missile and anti-satellite interceptors that will be adapted from sea-based to land-based use. In Pentagonese, the Aegis Ashore component of the Phased Adaptive Approach for progressively longer-range missiles in Eastern Europe, ones which in the third phase could cripple Russia’s ability to launch a retaliatory response to a first strike.
This February 27 the now late Polish President Lech Kaczynski ratified a Status of Forces Agreement (SOFA) with the U.S. for the stationing of the latter’s troops on his nation’s soil.
On March 5 the Polish armed forces launched combat training exercises with the participation of "scores of U.S. Army soldiers." 
Going backward in time, in August of 2008 the U.S. signed an agreement with Poland which includes a "commitment for both states to come to each other’s assistance in case of military threats."  What certainly appears to be a mutual defense pact.
In 2002 Poland signed the largest military purchase agreement in its history: 48 F-16 multirole jet fighters, the first of which were delivered in 2006. They were the first U.S. fighters provided to a former Eastern Bloc nation.
In 2005 Poland became the first former Warsaw Pact state to assume control of the NATO Baltic air patrol established immediately after Estonia, Latvia and Lithuania joined the bloc in 2004. Polish warplanes took over from U.S. F-16 Fighting Falcons. Poland will again take control of the mission next month with four warplanes operating out of and 100 troops stationed at the Lithuanian Air Force base at Siauliai.
In 2007 the Pentagon announced plans to sell Romania 48 F-16s as well, 24 new and 24 refurbished older jet fighters, for $4.5 billion, without doubt the most expensive military purchase in that nation’s history also. Late last month the Romanian government confirmed its decision to buy the 24 second-hand F-16s, beating out competition from France’s Dassault (Rafale), Sweden’s SAAB (Grippen) and the European Aeronautic Defence and Space Company (Eurofighter).
Early this month U.S. arms manufacturer Textron disclosed it would jointly produce armored vehicles with a Romanian counterpart, as "Romania is planning to buy about 800 armored vehicles."  Romania’s NATO accession has proven invaluable for the Pentagon’s plans to expand deployments and operations from Europe to the east and the south and has been correspondingly lucrative for U.S. arms firms.
In March the Czech press revealed that "the Czech Republic is in discussions with the Obama administration to host a command center for the United States’ altered missile-defense plan." 
During the recently-concluded Nuclear Security Summit in Washington, DC where a number of decidedly unrelated agreements were reached including one with which the U.S. secured the right for military overflights from Kazakhstan , Czech Defense Minister Martin Bartak disclosed that his meetings in the American capital included one with Under Secretary of Defense for Policy Michele Flournoy and Under Secretary of State for Arms Control Ellen Tauscher, the latter a long-time advocate for and organizer of U.S. missile shield projects in Eastern Europe.
In addition to being pressured by his American interlocutors to provide more troops for the Afghan war, Bartak said the three talked about Washington’s interceptor missile system, specifically that "The Czech Republic may be a part of a new warning system against possible enemy missile attacks," personally adding that "the Czech Republic is prepared to participate in the system." To demonstrate that the deliberations were not of an abstract nature, the Czech defense chief also mentioned the "sharing of data from commanding and observing elements placed in two locations in the Czech Republic." 
Both the missile shield command center and the surveillance sites would include, in fact would be run by, American military personnel.
As will the (presumably) Standard Missile-3 interceptor missile sites offered to the U.S. in February by the Romanian and Bulgarian governments.
In Hungary, the world’s first multi-national strategic airlift operation was activated last July at the Papa Air Base. Although established under the auspices of NATO and jointly operated by twelve NATO and all-but-acknowledged NATO members – the U.S., Bulgaria, Estonia, Hungary, Lithuania, the Netherlands, Norway, Poland, Romania and Slovenia and Finland and Sweden – it is not under NATO command. It is an American project for the expanding war in Afghanistan with, as one U.S. officer assigned to the command put it, a "24-hours-a-day, seven-days-a-week" operation which "recently moved 2.1 million pounds of equipment essential to surge operations supporting the International Security Assistance Force in Afghanistan." 
U.S. Air Force personnel are deployed there for the indefinite future, as their fellow service members are in Bulgaria and Romania and soon will be in Poland.
In former Soviet space, in addition to the participation of American warplanes over the Baltic nations of Estonia, Latvia and Lithuania and the regular participation of troops in NATO Partnership for Peace and other war games in Ukraine, Azerbaijan and Armenia, the Pentagon has established a permanent presence in Georgia since 2002, first with a Train and Equip Program and since then with U.S. Marines there on an ongoing basis and a steady parade of Marine commanders in and out of the capital of Tbilisi. Most recently Lieutenant General Richard F. Natonski, Commander of U.S. Marine Corps Forces Command, and Brigadier General Paul W. Brier, Commander of U.S. Marine Corps Forces Europe (and of U.S. Marine Forces Africa) earlier this month. 
U.S. troops and equipment were in that nation during the five-day war with Russia in August of 2008 and are there now.
The U.S. guided missile frigate USS John L. Hall arrived at the Georgian Black Sea port of Poti on April 14 for a week of joint exercises.
In turbulent Kyrgyzstan the U.S. runs one of the largest transit operations for the war in Afghanistan. In March U.S. Special Representative for Afghanistan and Pakistan Richard Holbrooke stated that 35,000 American troops pass through the air base at Manas each month on their way to and from Afghanistan, and U.S. Central Command has acknowledged that the number reached 50,000 last month.
In neighboring Kazakhstan, the U.S. gained military flyover rights with the government on April 11 which include for the first time the transit of combat troops and lethal military equipment.
A Kyrgyz news source revealed that in discussions between Kazakh President Nursultan Nazarbayev, U.S. President Obama and his main Russian and Eurasian hand Michael McFaul, the last-named proposed the establishment of an American military base in Kazakhstan to either supplement or replace if need be the Transit Center at Manas in Kyrgyzstan. 
Retired Russian general Leonid Ivashov has stated that new U.S.-Kazakh military cooperation plans "threaten the interests of Russia and other countries, notably China and especially Iran against which the United States is preparing a military operation," particularly if as seems increasingly likely the U.S. opens "a military base in Kazakhstan similar in size to the Kyrgyz facility." 
In the post-Cold War period the Pentagon through bilateral agreements, but even more so through NATO partnerships, has ensconced itself in former Warsaw Pact and Soviet nations from the Baltic Sea to the Black Sea to Central Asia. From the Balkans to the Chinese border.
. NATO’s Sixty Year Legacy: Threat Of Nuclear War In Europe, Stop Nato, March 31, 2009
NATO’s Secret Transatlantic Bond: Nuclear Weapons In Europe, December 3, 2009
. Bulgaria, Romania: U.S., NATO Bases For War In The East, Stop NATO, October 24, 2009
Black Sea: Pentagon’s Gateway To Three Continents And The Middle East, Stop NATO, February 21, 2009
. Bulgaria, Romania: U.S., NATO Bases For War In The East, Stop NATO, October 24, 2009
. U.S., NATO Intensify War Games Around Russia’s Perimeter, Stop NATO, March 6, 2010
. Kazakhstan: U.S., NATO Seek Military Outpost Between Russia And China, Stop NATO, April 13, 2010
. U.S. Marines In The Caucasus As West Widens Afghan War, Stop NATO, September 3, 2009