2,787 research outputs found

    Book Review: The Good Captain: A Personal Memoir of America at War

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    Author: R. D. Hooker Jr. Reviewed by Joseph J. Collins, PhD, retired US Army colonel Retired Army colonel Rich Hooker’s The Good Captain is a memoir spanning the Cold War through the Global War on Terror. Hooker’s deployments take up the bulk of the book and include Grenada with the 82nd Airborne Division, Somalia to work with legendary Ambassador Bob Oakley, Zaire to coordinate humanitarian operations in Rwanda, Bosnia, and Kosovo as a parachute infantry battalion commander, the Sinai Peninsula for peacekeeping operations, command of the Dragon Brigade in Iraq and, in his last year of service, Afghanistan with the 82nd Airborne Division. His description of the politics of the high command bears close examination.https://press.armywarcollege.edu/parameters_bookshelf/1014/thumbnail.jp

    AFGHANISTAN: THE EMPIRE STRIKES OUT

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    Defeat in Afghanistan: An Autopsy

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    Policy initiatives in the Trump administration and the Biden-Harris administration significantly accelerated the Taliban’s victory in Afghanistan. This article supports the conclusion that the major factors in this defeat were the historical difficulty in governing Afghanistan, the Afghan republic’s two inefficient and corrupt governments, an ineffective US strategy, operational shortcomings by US forces, an ineffective Afghan military, Pakistan’s duplicitous policy, and the strength and determination of the Taliban. This article rejects the claim that the United States’ nation-building effort was a major factor in its defeat and concludes with a discussion of lessons encountered

    The Soviet Invasion of Afghanistan: Methods, Motives, and Ramifications

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    The invasion of Afghanistan was the Soviet Union\u27s most expensive and direct involvement in a Third World conflict and many reasons have been suggested for it

    THE SOVIET-AFGHAN WAR: THE FIRST FOUR YEARS

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    Defeat in Afghanistan: An Autopsy

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    Policy initiatives in the Trump administration and the Biden-Harris administration significantly accelerated the Taliban victory in Afghanistan. This article supports the conclusion that the major factors in this defeat were the historical difficulty in governing Afghanistan, the Afghan republic’s two inefficient and corrupt governments, an ineffective US strategy, operational shortcomings by US forces, an ineffective Afghan military, Pakistan’s duplicitous policy, and the strength and determination of the Taliban. This article rejects the claim that the United States’ nation-building effort was a major factor in its defeat and concludes with a discussion of lessons encountered

    Ionization Sources and Physical Conditions in the Diffuse Ionized Gas Halos of Four Edge-On Galaxies

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    Deep long-slit spectra of the diffuse ionized gas halos of the edge-on spiral galaxies NGC 4302 and UGC 10288 are presented. These data, along with previously presented data for NGC 5775 and NGC 891, are used to address the issue of how DIG halos are energized. Composite photo-ionization/shock models are generally better at explaining runs of line ratios in these galaxies than photo-ionization models alone. Models of line ratios in NGC 5775 require a greater contribution from shocks for filamentary regions than for non-filamentary regions to explain the run of [OIII]/Halpha. In either case, the [SII]/[NII] ratio is not well fit by the models. Composite models for UGC 10288 are successful at reproducing the run of [SII]/[NII] for all but the the highest values of [NII]/Halpha; however, the run of [OIII]/Halpha vs. [NII]/Halpha does not show any discernible trend, making it difficult to determine whether or not shocks make a contribution. We also examine whether the data can be explained simply by an increase in temperature with z in a pure photo-ionization model. Runs of [SII]/Halpha, [NII]/Halpha, and [SII]/[NII] in each of the four galaxies are consistent with such an increase. However, the runs of [OIII]/Halpha vs. z in NGC 5775 and UGC 10288 require unusually high ionization fractions of O^{++} that can not be explained without invoking a secondary ionization source or at the very least a much higher temperature for the [OIII]-emitting component than for the [SII]- and [NII]-emitting component. An increase in temperature with z is generally more successful at explaining the [OIII]/Halpha run in NGC 891.Comment: 42 pages in aaspp4.sty format. This includes the 19 figures. Reference added. Accepted for publication in Ap

    Highly Ionized High-Velocity Clouds toward PKS 2155-304 and Markarian 509

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    To gain insight into four highly ionized high-velocity clouds (HVCs) discovered by Sembach et al. (1999), we have analyzed data from the Hubble Space Telescope (HST) and Far Ultraviolet Spectroscopic Explorer (FUSE) for the PKS 2155-304 and Mrk 509 sight lines. We measure strong absorption in OVI and column densities of multiple ionization stages of silicon (SiII/III/IV) and carbon (CII/III/IV). We interpret this ionization pattern as a multiphase medium that contains both collisionally ionized and photoionized gas. Toward PKS 2155-304, for HVCs at -140 and -270 km/s, respectively, we measure logN(OVI)=13.80+/-0.03 and log N(OVI)=13.56+/-0.06; from Lyman series absorption, we find log N(HI)=16.37^(+0.22)_(-0.14) and 15.23^(+0.38)_(-0.22). The presence of high-velocity OVI spread over a broad (100 km/s) profile, together with large amounts of low-ionization species, is difficult to reconcile with the low densities, n=5x10^(-6) cm^(-3), in the collisional/photoionization models of Nicastro et al. (2002), although the HVCs show a similar relation in N(SiIV)/N(CIV) versus N(CII)/N(CIV) as high-z intergalactic clouds. Our results suggest that the high-velocity OVI in these absorbers do not necessarily trace the WHIM, but instead may trace HVCs with low total hydrogen column density. We propose that the broad high-velocity OVI absorption arises from shock ionization, at bowshock interfaces produced from infalling clumps of gas with velocity shear. The similar ratios of high ions for HVC Complex C and these highly ionized HVCs suggest a common production mechanism in the Galactic halo.Comment: 38 pages, including 10 figures. ApJ, 10 April, 2004. Replaced with accepted versio

    Global Analysis of Fragmentation Functions for Eta Mesons

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    Fragmentation functions for eta mesons are extracted at next-to-leading order accuracy of QCD in a global analysis of data taken in electron-positron annihilation and proton-proton scattering experiments. The obtained parametrization is in good agreement with all data sets analyzed and can be utilized, for instance, in future studies of double-spin asymmetries for single-inclusive eta production. The Lagrange multiplier technique is used to estimate the uncertainties of the fragmentation functions and to assess the role of the different data sets in constraining them.Comment: 11 pages, 8 figures, updated reference
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