The US has now an active force structure of just 39 maneuver brigades (Army and Marines); only about 13 are combat ready; to add more brigades would require cannibalization of about 25% of the remaining 26 active units

Israel Versus Anyone: A Military Net Assessment of the Middle East. Kenneth S. Brower. The Begin-Sadat Center for Strategic Studies. Mideast Security and Policy Studies No. 178, Aug 2020. https://besacenter.org/wp-content/uploads/2020/07/178web.pdf


Most Israelis and Americans view the US as the ultimate guarantor
of Israeli security. They assume that in a dire emergency, US
conventional military forces would be able to rescue Israel before it
faced total defeat. They also believe that US training and military
equipment is absolutely vital to Israeli military power.
These widely held assumptions are divorced from reality. The simple
and unarguable truth is that for decades the US military has lacked the
ability to quickly project conventional ground and air forces into the
Middle East that would be able to successfully defend Israel. This has
been true for about 50 years.5

The US Army and US Marine Corps combined now have an active
force structure of just 39 maneuver brigades, of which only about 13
are combat ready. It would require many weeks to bring a portion of
the remaining 26 active maneuver brigades to combat ready status.
Achieving this would require cannibalization of about 25% of the
remaining active units in order to bring the others to full strength.
US reserve National Guard maneuver brigades would each require
about five months for mobilization, retraining, and deployment.
These National Guard reserve units are thus irrelevant to any Israeli
rescue scenario.6

The ability of the US military to deploy forces over long distances has
declined in the last 30 years because of a lack of investment in large
specialized roll-on roll-off ships. Many of the existing US reserve
merchant marine ships dedicated to military use are overage and have
been poorly maintained. Based on the deployment times achieved
during Operation Desert Storm, it is estimated that within about three
weeks the US could project two light infantry paratroop brigades
into Israel by air, plus one Marine infantry brigade transferred by
forward deployed USN amphibious ships and pre-loaded forward-based maritime ships.

Given about nine weeks, the US would likely
be able to field nine maneuver brigades in the Middle East consisting
of three paratroop, three Marine, and three heavy armored brigades.
Consequently, it would require about nine weeks for the US military to
generate roughly 15% of the IDF’s ground force mobilizable order of
battle. These US forces would only deploy about 10% of the number
of armored fighting vehicles the IDF can field.7

The USAF has a very limited number of combat aircraft currently
deployed in Europe. With air-to-air refueling, it is estimated that
these aircraft might be able to sustain the generation of about 90
sorties a day in support of Israel. But these few sorties, which only
represent 5% of Israeli wartime capability, could only be generated
if the host country where these aircraft are based were to allow them
to be operated in support of Israel. In the past, this approval has not
always been provided. Neither the USN nor USMC currently have
any operational combat aircraft based on aircraft carriers or large
amphibious ships that are normally deployed in the Mediterranean
within range of Israel.8

If numerous European airfields were to be made available for use
by the USAF, with appropriate host nation approval, it is estimated
that within 30 days the US could likely shift about 15 additional
fast jet squadrons into Europe. This would potentially raise the
number of daily USAF fast jet sorties generatable to about 450 per
day. However, projecting aircraft over great distances onto existing
airfields sounds far simpler than it is. Maintaining these aircraft
requires extensive specialized ground support equipment. Generating
sorties also requires vast quantities of fuel, munitions and spare parts.
The personnel that command, fly, maintain, and support these aircraft
all require housing and security. Unless European military airfields
are almost totally pre-prepared and fully stocked with ground support
equipment and consumables, which they generally are not, it requires
substantial sealift to transfer everything but the aircraft and personnel
overseas—and sealift takes time.

It should be noted that the generation of 450 daily long-range combat
sorties would also require the forward basing of at least 72 to 96
additional USAF aerial tankers in Europe. Without the provision of
additional forward-based air-to-air refueling tankers, European-based
USAF aircraft would be largely useless in support of Israel.
The USN could likely deploy two carrier battle groups in the
Mediterranean within 30 days. Each USN carrier currently carries
only 44 F-18 combat aircraft. Many of these have to be dedicated to
the generation of defensive combat air patrols and/or buddy air-toair tanking.
Depending on the selected stand off distance from shore,
each carrier can only generate 25 to 50 offensive fast jet sorties per
day. The USMC would likely be able to shift one air wing forward,
including up to 30 F-35B or AV-8B VSTOL aircraft operating from
two or three LHDs/LHAs. These vulnerable unarmored ships would
have to operate far offshore. The sea-based Marine VSTOL aircraft,
which have very limited range, would, therefore, likely generate a
very low daily sortie rate. Conventional Marine F-18 combat aircraft
would, like all USAF aircraft, have to be based at European airfields.
Marine fast jet aircraft would likely generate a daily sortie rate similar
to European-based USAF aircraft and would require additional aerial
tanker support.

To summarize: Given 30 days to mobilize and deploy, and being
provided with access to about 12 large European military air bases,
all with the host nations’ approval for use in support of Israel, and the
deployment of a large number of USN aircraft carriers and amphibious
ships, the three combined US military air forces could only sustain the
generation of about one-third the number of daily combat sorties that
can be generated by the IAF on day one.