South Vietnam President Ngo Dinh Diem was a paranoid man with an enormous ego.  In accepting U.S. military and financial aid, Diem agreed to allow the American military to train and direct the South Vietnamese military efforts against the Communists.  However, Diem feared sharing success with his own officers, even when the American military recommended promotions.  Rather than promote and share the limelight of military success with his generals and his army, Diem would often ridicule them because he feared they would receive too much attention and power.  In one case, Diem summoned a colonel who had been recommended for a promotion and told him that his promotion would be denied if he incurred any more casualties.  The effect of this was that the South Vietnamese military was being told to do one thing by the U.S. military advisors, while fearing Diem at the same time.  Diem was corrupt, oppressive, and difficult to work with.  Unfortunately, his attitude clearly affected the way his men fought in battle.  U.S. advisors found it difficult to work with ARVN troops at times and reports of their abilities are mixed, depending on which veteran one interviews, or who is doing the writing.  Suffice it to say that it would be unfair to make a group judgment about their effort and ability.  Some were more effective and courageous than others.  To overstate the obvious, though, the South Vietnamese troops were no match for their North Vietnamese counterparts without significant U.S. aid and advise.

Following is a review a few key battles.  This is not presented as a comprehensive list, rather just some of the highlights with brief comments.

Jan. 2, 1963 - Ap Bac, near the Cambodian border:
  ARVN forces with 51 U.S. advisors attempted to capture a Communist radio center.
  Expecting an easy victory, ARVN forces were surprised to find about 400 Vietcong
  troops at Ap Bac.  Still, the ARVN had superior numbers and the support of U.S.
  helicopters.  ARVN military leaders, fearing reprisals from Diem, refused to listen to
  U.S. advisors and delayed actions.  ARVN forces were not aggressive and were
  defeated.  Three U.S. advisors were killed, six were wounded, and five helicopters
  were destroyed.  Results of this battle convinced the U.S. military that they needed to
  take full control of the war.  This also opened a widening rift between Vietnamese
  military leaders, the U.S., and President Diem.  Ten months later, Diem was
  overthrown and murdered in a military coup.

Aug. 2, 1964 - North Vietnamese patrol boats fire on USNS Maddox in Gulf of Tonkin
  The USNS Maddox was patrolling in the Gulf of Tonkin outside North Vietnam’s
  when three North Vietnamese torpedo boats approached at high speed.
  Warning shots did not stop the attack, so the Maddox destroyed one of the boats and
  damaged a second. Two fired torpedoes missed the Maddox by 200 yards.

Aug. 4, 1964 - Apparent attack of five torpedo boats against USNS Maddox and
                          USNS C. Turner Joy in Gulf of Tonkin:
  On a stormy evening in the Gulf of Tonkin an inexperienced Maddox radar man
  reported what he judged to be five torpedo boats 36 nautical miles away and
  heading toward the ships.  The ships called for air support and opened fire.  Initial
  reports from the ships indicated two boats were sunk and two were damaged.
  However, U.S. intelligence later revealed that the apparent enemy ships shown on
  the radar were actually radar blips.  Pilots, including the highly respected and
  decorated James Stockdale, reported they saw nothing in the waters of the Gulf of
  Tonkin that night.
  Further, the North Vietnamese contend to this day that they did not have boats in the
  Gulf of Tonkin that night.  However, President Johnson was convinced by field
  commanders that an attack had taken place.  Johnson ordered an air attack against
  North Vietnamese bases, which resulted in the destruction of 25 torpedo boats and
  an oil storage depot.  Infuriated and wanting to show public support for President
  Johnson even though it was an election year, Congress quickly approved the Gulf of
  Tonkin Resolution on August 11, 1964.  This resolution gave the president the
  authority to take any action, including military force, he deemed necessary to repel
  any armed attack against the United States or to assist any member of the Southeast
  Asia Treaty Organization, including South Vietnam.  This critical resolution, based on
  conflicting reports and unclear information, essentially gave the president the right to
  make war without a declaration of war.  Only Congress can declare war and neither
  Congress nor the President wanted to pursue that because it might have caused
  both China and the Soviet Union to declare war against the United States.
  Intelligence reports and historical reviews of the Gulf of Tonkin incident indicate that
  there was likely no attack against the Maddox and C. Turner Joy on the evening of
  August 4, 1964.  Irrespective, the result remains the same, the United States was
  about to go to war without declaring it.  Consider this quote by President Johnson
  prior to his decision to send in ground forces in 1965: “For all I know, our Navy was
  shooting at whales out there.”

Jan/Feb, 1965 - Vietcong attack several US bases:
  The North Vietnamese Army and the Viet Cong persistently attacked U.S. bases and
  sites where U.S. advisors were known to gather.  These types of attacks included
  planting bombs in cars, on streets, or in buildings, hit and run guerrilla tactics,
  sending in a barrage of mortars, and all out attacks.
 

Mar. 2, 1965 -- Rolling Thunder -- sustained bombing of North Vietnam:
  Concerned about the way the war was progressing, President Johnson approved
  Operation Rolling Thunder.  This sustained bombing of North Vietnam military
  positions and the Ho Chi Minh Trail involved over 200,000 in three years. Judged by
  many to be relatively ineffective in stopping the flow of men and materiel into the
  south.  Still, this operation showed the U.S. would not sit idly by and watch casualties
  grow without a response.  During Operation Rolling Thunder, the United States
  dropped more bombs on North Vietnam than it had on Europe in all of World War II.

Mar. 8, 1965 - first combat troops land at Danang
  Though not a battle per se, this key event was a major move on the part of the United
  States.  Led to many battles involving significantly more U.S. troops and casualties.

Dec., 1967 -- Communist attack on Khe Sanh - major US base:
   Approximately 20,000 North Vietnamese were spotted gathering outside of Khe
  Sahn, site of a major U.S. base.  Skirmishes were fought as U.S. forces and materiel
  were flown in.  On January 21, 1968 the NVA pounded Khe Sanh with mortars and
  artillery.  The fighting at Khe Sanh was perhaps the most intense of the entire war,
  involving hand-to-hand combat at times.  U.S. marines held off the siege after 77
  days of fighting.  American casualties totaled 205 killed, 443 wounded, 2 missing.
  North Vietnamese casualties totaled 807 killed. Over 23,000 artillery rounds were
  fired, 1,170 sorties were flown dropping over 3 million pounds of explosives, 611,000
  pounds of napalm, and 5,000 bombs. Incredibly, not long after the costly U.S. victory,
  the Khe Sanh base was abandoned.   General Westmoreland had described the
  Khe Sanh base as critical to the U.S. effort and he believed that the siege of Khe
  Sanh was the major effort by the NVA. In fact, the Khe Sanh siege appears to have
  been part of a larger plan by the Communists to mount an all out offensive, Tet.

Jan. 31, 1968: Tet Offensive
  Tet is the most important holiday in Vietnam and there was an unofficial cease fire in
  place.  At 2:45 a.m. on January 31, 1968 the American Embassy in Saigon was
  attacked.  This was the start of perhaps the best known battle of the Vietnam War.
  More than 70,000 North Vietnamese and Viet Cong troops attacked over a hundred
  cities, villages, and military sites throughout South Vietnam.  Among the many battles
  fought during the Tet Offensive, one of the more brutal battles occurred in the city of
  Hue.  In Hue, civilians were tortured and executed by the thousands before the city
  was finally liberated.  Within weeks the Communists were badly beaten.  About
  45,000 NVA and VC troops were killed and nearly 7,000 prisoners were taken.  The
  U.S. forces suffered 1,536 deaths, 7,764 wounded, and 11 missing in action.  South
  Vietnamese forces had 2,788 killed and 8,299 wounded.  Innocent civilians were
  tortured and killed: 14,000 killed, 24,000 wounded, over 600,000 were left homeless.
  Another casualty of this battle was American public opinion, which turned
  dramatically against the war.

May, 1969 - Hill 937 - Battle of Ap Bia Mountain - aka Hamburger Hill (near Laos):
  The war changed after Tet and Richard Nixon was elected President.  After losing the
  Tet Offensive so decisively, the Communists were wary of U.S. firepower, and they
  also knew the Americans would eventually leave as the gradual withdrawal of U.S.
  troops had been announced.  In 1969, the Communists normally avoided large
  battles.  They chose instead to hit, then run and hide in Cambodia and Laos.  To try
  to halt the Communist attacks, the U.S. would send units out to search and destroy
  the enemy.  During one of their missions, the 101st Airborne Division attacked
  Communist forces on a steep hill in the A Shau Valley.  The battle for this hill, known
  as Hill 937, was incredibly fierce as the NVA and VC decided to stand and fight due
  to their favorable position on the hill.  American forces relentlessly attacked the
  enemy for six days, at times crawling on their stomachs up the hill.  Eventually, U.S.
  forces took the hill, but casualties were high, causing even more political and public
  dissent about the war.  American losses were 46 killed and 400 wounded and
  NVA/VC losses were 633 killed.  Within days of winning the battle for Hill 937, the
  Americans once again abandoned the area, which further inflamed public outrage.
  Military leaders responded that they were not fighting for geography, rather, they just
  wanted to find and kill the enemy.

April 30, 1970 - US & ARVN invade Cambodia
  This is discussed in greater length in another lesson.  U.S. and ARVN forces
  attacked NVA/VC sanctuaries in Cambodia.  Succeded in capturing a great deal of
  enemy materiel, but set off a firestorm of protest in the United States.

Mar. 31, 1972 - NV Easter Offensive across 17th Parallel
  In 1972, peace negotiations were progressing in Paris and American troop
  withdrawals continued.  The North Vietnamese took the opportunity to launch their
  biggest offensive since Tet.  They stormed across the DMZ and easily pushed South
  Vietnamese forces and civilians further south.  Thousands of civilians fled in a
  chaotic refugee escape and many South Vietnamese troops abandoned their
  positions.  Eventually, the attack was repelled with U.S. support, but it showed
  glaring weaknesses in the abilities of the ARVN without the United States being
  actively involved.  The attack also further hampered peace talks.