232 research outputs found
Professionalism Under Fire: Canadian Implementation of the Medak Pocket Agreement, Croatia 1993
For many Canadians, the Somalia Affair became a symbol of their armed forces in the 1990s. Intense media coverage of a Somali teenâs murder by Canadian paratroopers, its cover-up by senior bureaucrats and officers at National Defence Headquarters and a series of subsequent scandals shook public confidence in the nationâs military institutions. Negative coverage particularly in the first half of the 1990s created an image of military incompetence and unprofessionalism, vividly captured in letters to the editor to major newspapers across the country. In recent years that image was balanced with more positive ones of Canadian Forces personnel protecting the peace in the Former Yugoslavia, Africa, and East Timor. Nevertheless, the spectre of Somalia still lingers in the minds of many both in and out of uniform
Operations of 1 Canadian Infantry Divisional Artillery, 24 August-22 September 1944
In January 1944 1st Canadian Infantry Division reverted to command of I Canadian Corps after seven months of campaigning in Sicily and Italy under a British Corps. The story of the divisionâs resentment toward the level of paperwork foisted on them by H.D.G. Crerarâs untried corps headquarters is legendary. Modern military historians assume this rancour is indicative of a 1914â18 mindset among Second World War Canadian senior officers which prevented them from adapting to the fastâpaced nature of modern mechanized warfare in the 1940s.1 Ironically, much of that âpaperâpushingâ appears to have contributed to the Canadian Armyâs victories over German forces in the great battles of 1944â45.
Among the most labourious administrative chores were the operational narratives and lessons learned reports requiring battle participants to analyze recent actions and draw conclusions for improving combat efficiency. These reports do indeed date back to the Great War. Most First World War historians agree that such documents were a key ingredient to the remarkable success of the Canadian Corps in 1915â1918.2
The following report was prepared by the 1st Canadian Divisional Artillery staff in late September 1944, during the brief pause between the breakthrough of the Gothic and Rimini Lines and the subsequent pursuit into the Po Valley. In the weeks prior to that pause, I Canadian Corps suffered their heaviest losses to date against the most determined German resistance encountered during the Italian Campaign. They also demonstrated remarkable military skill and professionalism, and won their greatest victories of the entire war.
Readers may note that the report is tightly focussed on exacting every possible ounce of combat power out of an already effective organization. Continual refinements to the AngloâCanadian system were essential given that Alliedforces in Italy usually possessed the barest minimum of resources necessary to accomplish their strategic mission of preventing German formations from withdrawing to more decisive fronts. Similar reports are found in the war diaries of all units and formations in the Canadian Army in the Second World War. What is most significant about this process is the rapidity with which recommended improvements were put into practice during subsequent operations
Robust Magnetic Order Upon Ultrafast Excitation of an Antiferromagnet
The ultrafast manipulation of magnetic order due to optical excitation is governed by the intricate flow of energy and momentum between the electron, lattice, and spin subsystems. While various models are commonly employed to describe these dynamics, a prominent example being the microscopic three temperature model (M3TM), systematic, quantitative comparisons to both the dynamics of energy flow and magnetic order are scarce. Here, an M3TM was applied to the ultrafast magnetic order dynamics of the layered antiferromagnet GdRh2Si2. The femtosecond dynamics of electronic temperature, surface ferromagnetic order, and bulk antiferromagnetic order were explored at various pump fluences employing time- and angle-resolved photoemission spectroscopy and time-resolved resonant magnetic soft X-ray diffraction, respectively. After optical excitation, both the surface ferromagnetic order and the bulk antiferromagnetic order dynamics exhibit two-step demagnetization behaviors with two similar timescales (<1 ps, âŒ10 ps), indicating a strong exchange coupling between localized 4f and itinerant conduction electrons. Despite a good qualitative agreement, the M3TM predicts larger demagnetization than the experimental observation, which can be phenomenologically described by a transient, fluence-dependent increased NĂ©el temperature. The results indicate that effects beyond a mean-field description have to be considered for a quantitative description of ultrafast magnetic order dynamics
Ultrafast Laser-Induced Melting of Long-Range Magnetic Order in Multiferroic TbMnO3
We performed ultrafast time-resolved near-infrared pump, resonant soft X-ray
diffraction probe measurements to investigate the coupling between the
photoexcited electronic system and the spin cycloid magnetic order in
multiferroic TbMnO3 at low temperatures. We observe melting of the long range
antiferromagnetic order at low excitation fluences with a decay time constant
of 22.3 +- 1.1 ps, which is much slower than the ~1 ps melting times previously
observed in other systems. To explain the data we propose a simple model of the
melting process where the pump laser pulse directly excites the electronic
system, which then leads to an increase in the effective temperature of the
spin system via a slower relaxation mechanism. Despite this apparent increase
in the effective spin temperature, we do not observe changes in the wavevector
q of the antiferromagnetic spin order that would typically correlate with an
increase in temperature under equilibrium conditions. We suggest that this
behavior results from the extremely low magnon group velocity that hinders a
change in the spin-spiral wavevector on these time scales.Comment: 9 pages, 4 figure
Robust Magnetic Order Upon Ultrafast Excitation of an Antiferromagnet
The ultrafast manipulation of magnetic order due to optical excitation is governed by the intricate flow of energy and momentum between the electron, lattice, and spin subsystems. While various models are commonly employed to describe these dynamics, a prominent example being the microscopic three temperature model M3TM , systematic, quantitative comparisons to both the dynamics of energy flow and magnetic order are scarce. Here, an M3TM was applied to the ultrafast magnetic order dynamics of the layered antiferromagnet GdRh2Si2. The femtosecond dynamics of electronic temperature, surface ferromagnetic order, and bulk antiferromagnetic order were explored at various pump fluences employing time and angle resolved photoemission spectroscopy and time resolved resonant magnetic soft X ray diffraction, respectively. After optical excitation, both the surface ferromagnetic order and the bulk antiferromagnetic order dynamics exhibit two step demagnetization behaviors with two similar timescales lt;1 ps, amp; 8764;10 ps , indicating a strong exchange coupling between localized 4f and itinerant conduction electrons. Despite a good qualitative agreement, the M3TM predicts larger demagnetization than the experimental observation, which can be phenomenologically described by a transient, fluence dependent increased N el temperature. The results indicate that effects beyond a mean field description have to be considered for a quantitative description of ultrafast magnetic order dynamic
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